Skip to main content

Concentration Converters

Convert between molar concentration units: mol/L (M), mmol/L (mM), µmol/L (µM), and nmol/L (nM). Critical for solution chemistry and biochemistry.

Concentration tells you how much solute is dissolved in a solution. Molarity (mol/L or M) is the standard unit in general chemistry, but biochemistry and pharmacology often use millimolar (mM), micromolar (µM), or nanomolar (nM) for dilute solutions. Converting between these scales is straightforward — they differ only by powers of 1000 — but getting the prefix wrong can mean a thousandfold error in your experiment.

108 Concentration Conversions

g/100mL to Percent w/v Converter

% w/v = g/100mL × 1

Convert g/100 mL to % w/v. The two units are numerically identical by definition — a percent w/v is nothing more than grams of solute per 100 mL of solution.

g/kg to PPM Converter

ppm = g/kg × 1000

Convert g/kg to ppm by multiplying by 1000. The factor falls cleanly out of 1 ppm = 1 g per 1,000,000 g = 1 mg/kg in any solid-matrix sample.

g/L to g/mL Converter

g/mL = g/L ÷ 1000

Convert g/L to g/mL by dividing by 1000. The decimal step that bridges bioreactor titer reports and the high-concentration density numbers downstream formulation runs in.

g/L to mg/mL Converter

mg/mL = g/L × 1 (numerically identical)

Convert g/L to mg/mL — numerically identical units. The 1000-fold scale-up in mass cancels the 1000-fold scale-up in volume.

g/L to Molarity Converter

M = g/L / MW (molar mass in g/mol)

Convert g/L to molarity by dividing by the molar mass. The standard step that turns a weighed-out concentration into the mol/L units stoichiometric calculations actually use.

g/L to Percent w/v Converter

% w/v = g/L ÷ 10

Convert g/L to % w/v by dividing by 10. The factor falls out of the % w/v definition: grams of solute per 100 mL of solution.

g/L to PPM Converter

ppm = g/L × 1000

Multiply by 1000. The factor only works cleanly because water-quality reports assume the solution density sits at roughly 1 g/mL — true for any dilute aqueous sample, false the moment you get into brines or concentrated acid.

g/mL to g/L Converter

g/L = g/mL × 1000

Convert g/mL to g/L by multiplying by 1000. The decimal step that bridges measured solution density and the per-liter form a molarity calculation reads in.

g/mL to kg/L Converter

kg/L = g/mL × 1 (numerically identical)

Convert g/mL to kg/L — numerically identical units. The 1000-fold scale-up in mass exactly cancels the 1000-fold scale-up in volume.

Grams per Liter to mg/L Converter

mg/L = g/L × 1000

Convert g/L to mg/L by multiplying by 1000. The clean prefix step between bench-stock concentrations and the mg/L units water-quality and trace-analysis reports use.

Grams per Liter to µg/L Converter

µg/L = g/L × 10⁶

Six prefix decades stand between g/L and µg/L. That's the gap between a bulk solution and the trace-level numbers ICP-MS reports — most of the conversion's work is just bookkeeping for the exponent.

kg/L to g/mL Converter

g/mL = kg/L × 1 (numerically identical)

Convert kg/L to g/mL — numerically identical units. The 1000-fold scale-up in mass exactly cancels the 1000-fold scale-up in volume.

mEq/L to mg/L Converter

mg/L = (mEq/L × atomic weight) ÷ valence

Convert mEq/L to mg/L by multiplying by atomic weight and dividing by valence. Comes up at the boundary of charge-based clinical electrolyte reporting and mass-based reagent specs.

mg/dL to mg/L Converter

mg/L = mg/dL × 10

Ten deciliters in a liter, so the conversion is just ×10. The everyday case is US clinical reporting (mg/dL) crossing into the SI mass-concentration units bioanalytical labs prefer (mg/L).

mg/dL to mmol/L Converter

mmol/L = (mg/dL × 10) / MW

US clinical labs report glucose, cholesterol, and creatinine in mg/dL; the rest of the world uses mmol/L. To bridge them, multiply by 10 (deciliter to liter) and divide by the analyte's molar mass.

mg/kg to Percent Converter

% = mg/kg ÷ 10000

Divide mg/kg by 10,000 to get percent w/w. Two scales of the same mass-fraction story: trace-contaminant data (mg/kg, ppm) on one side, bulk-composition reporting (%) on the other.

mg/kg to PPM Converter

ppm = mg/kg × 1 (mass/mass)

Convert mg/kg to ppm. The two are numerically identical for mass per mass analysis — the conversion is the bookkeeping step between analytical lab output and regulatory reporting.

mg/L to Grams per Liter Converter

g/L = mg/L / 1000

Convert mg/L to g/L by dividing by 1000. The clean prefix step that takes a trace-analysis result up to the bulk-preparation scale.

mg/L to mEq/L Converter

mEq/L = (mg/L × valence) ÷ atomic weight

Convert mg/L to mEq/L by multiplying by valence and dividing by atomic weight. Useful any time mass-based reagent specs and charge-based clinical electrolyte reporting have to agree.

mg/L to mg/dL Converter

mg/dL = mg/L ÷ 10

Convert mg/L to mg/dL by dividing by 10. The factor falls cleanly out of 1 dL = 0.1 L.

mg/L to Molarity Converter

mol/L = (mg/L) / (MW × 1000)

Convert mg/L to mol/L by dividing by (MW × 1000). Comes up at the boundary of mass-concentration analytical reports and the mol/L units stoichiometry actually uses.

mg/L to Percent Converter

% = mg/L × 0.0001

Convert mg/L to % w/v by dividing by 10,000. The factor falls cleanly out of the % w/v definition: g per 100 mL of solution.

mg/L to PPB Converter

ppb = mg/L × 1000

Convert mg/L to ppb by multiplying by 1000. For dilute aqueous solutions the equivalence is exact: 1 mg/L = 1 ppm = 1000 ppb.

mg/L to PPM Converter

ppm = mg/L × 1 (for dilute aqueous solutions)

Convert mg/L to ppm — an identity for dilute aqueous solutions, where the two labels describe the same concentration.

mg/L to µg/L Converter

µg/L = mg/L × 1000

Convert mg/L to µg/L by multiplying by 1000. The decimal step from bulk-source concentrations into the trace-level form environmental and clinical chemistry use.

mg/L to µg/mL Converter

µg/mL = mg/L × 1 (numerically identical)

Convert mg/L to µg/mL — numerically identical units. The 1000-fold scale-down in mass cancels the 1000-fold scale-down in volume.

mg/m³ to PPM (Air) Converter

ppm = (mg/m³ × 24.45) ÷ MW

Convert mg/m³ to ppm in air via ppm = (mg/m³ × 24.45) / MW. The 24.45 factor is the ideal-gas molar volume at 25 °C and 1 atm.

mg/mL to g/L Converter

g/L = mg/mL × 1 (numerically identical)

Convert mg/mL to g/L — numerically identical units. The 1000-fold scale-up in mass exactly cancels the 1000-fold scale-up in volume.

mg/mL to Percent w/v Converter

% w/v = (mg/mL) × 0.1

Convert mg/mL to % w/v by dividing by 10. The factor falls cleanly out of the % w/v definition: g per 100 mL of solution.

Micromolar to Millimolar Converter

mM = µM / 1000

Convert micromolar to millimolar — a thousand-fold step that sits between the assay plate and the stock bottle. Formula, worked examples, and a table of common values.

Micromolar to Molar Converter

M = µM / 1000000

Convert micromolar to molar by dividing by 10⁶. The million-fold step that takes assay-scale concentrations back into the bulk-stock units used for dilutions.

Micromolar to Nanomolar Converter

nM = µM × 1000

Convert micromolar to nanomolar by multiplying by 1000. The scale-up you need when a working concentration has to be compared against a tight binding constant.

Micromolar to Picomolar Converter

pM = µM × 10⁶

µM × 10⁶ = pM. Six orders of magnitude, mostly used when you need to talk about an early screening hit and a late-stage optimized lead in the same sentence.

Milliequivalents/L to mmol/L Converter

mmol/L = mEq/L ÷ valence

Convert mEq/L to mmol/L by dividing by the ion's valence. For monovalent ions the values are identical; for divalent the mmol figure is half.

Millimolar to Micromolar Converter

µM = mM × 1000

Convert millimolar to micromolar — a thousand-fold step you make every time a stock solution has to meet a working concentration. Formula, worked examples, and a table of common values.

Millimolar to Molar Converter

M = mM ÷ 1000

Convert millimolar to molar by dividing by 1000. The reverse of how most buffer recipes get written — drop the factor of 1000 when you need to plug into an equation that expects mol/L.

Millimolar to Molarity Converter

M = mM / 1000

Convert millimolar to molar concentration by dividing by 1000. The clean step between buffer-recipe values in mM and the M units stock-solution math expects.

Millimolar to Nanomolar Converter

nM = mM × 10⁶

Convert mM to nM by multiplying by 10⁶. A six-decade SI prefix jump between cell-culture buffer concentrations and lead-compound IC50 values.

Millimolar to Picomolar Converter

pM = mM × 10⁹

Convert mM to pM by multiplying by 10⁹. A jump of nine prefix decades, the gap between cell-buffer concentrations and the picomolar binding constants therapeutics target.

Milliosmolarity to Osmolarity Converter

Osm/L = mOsm/L ÷ 1000

Convert mOsm/L to Osm/L by dividing by 1000. The milli prefix step bridging clinical osmolality readings and the formal SI base unit.

mL/L to Percent v/v Converter

% v/v = mL/L ÷ 10

Convert mL/L to % v/v by dividing by 10. The factor falls cleanly out of the % v/v definition: mL of solute per 100 mL of solution.

mmol/L to mg/dL Converter

mg/dL = mmol/L × MW ÷ 10

Convert mmol/L to mg/dL via mg/dL = mmol/L × MW / 10. Used at the handoff between SI clinical-chemistry data into US-convention mass-based reporting.

mmol/L to Milliequivalents/L Converter

mEq/L = mmol/L × valence

Convert mmol/L to mEq/L by multiplying by ion valence. Used when SI clinical-chemistry data must meet the per-charge form bedside electrolyte management expect.

mol/(L·min) to mol/(L·s) Reaction Rate Converter

mol/(L·s) = mol/(L·min) ÷ 60

Convert reaction rates from per-minute to per-second by dividing by 60. The SI standard uses seconds, so the conversion is the routine step before publishing kinetics data.

mol/(L·s) to mol/(L·min) Reaction Rate Converter

mol/(L·min) = mol/(L·s) × 60

60 seconds in a minute — that's the whole conversion. Trivial arithmetic, but the bridge between fast transient-kinetics work (stopped-flow, T-jump) and steady-state biochemistry where Vmax is tabulated per minute.

Molar to Micromolar Converter

µM = M × 1000000

A factor of a million separates molar from micromolar. That's the gap between the M-scale stocks chemists keep on the bench and the µM concentrations actually used in assays and pharmacology.

Molar to Millimolar Converter

mM = M × 1000

Convert molar to millimolar by multiplying by 1000. The step that takes a concentrated stock down to a working buffer concentration — formula, examples, and a common-values table.

Molar to Millimolar Converter

mM = M × 1000

Convert molar to millimolar by multiplying by 1000. The decimal step from bottle-label stock concentrations to the mM working concentrations buffers and assays use.

Molar to Nanomolar Converter

nM = M × 10⁹

Convert molar to nanomolar by multiplying by 10⁹. The scale bridge between bench stock solutions and the low-nM concentrations where drug potency and receptor binding are reported.

Molar to Picomolar Converter

pM = M × 10¹²

Convert molar to picomolar by multiplying by 10¹². A jump of twelve orders of magnitude — from shelf-stock concentration down to the tightest binding regime that routinely gets measured.

Molarity to g/L Converter

g/L = M × MW (molar mass in g/mol)

Convert molarity to grams per liter by multiplying by the molar mass. The step that turns a mole-based recipe into the mass a balance has to weigh out.

Molarity to mg/L Converter

mg/L = mol/L × MW × 1000

Convert mol/L to mg/L by multiplying by molecular weight × 1000. Used when per-mole molar concentration must meet the mass-based form environmental and analytical chemistry expect.

Molarity to Moles Converter

moles = molarity (M) × volume (L)

Convert molarity and volume to moles via n = M × V. The core relationship behind solution preparation, titrations, and dilution math.

Molarity to Normality Converter

N = M × n (where n depends on the reaction)

Convert molarity to normality for acid-base and redox titrations. Normality is molarity weighted by the number of equivalents — n per H⁺, OH⁻, or electron transferred.

Molarity to PPM Converter

ppm = M × MW × 1000 (for dilute aqueous solutions)

Convert molarity to ppm by multiplying by molar mass and 1000. A unit step between bench-scale mol/L concentrations and the ppm units water-quality and trace-analysis reports use.

Moles to Molarity Converter

M = mol / V (L) — molarity needs a solution volume; this is not a pure unit conversion

This isn't strictly a unit conversion — molarity is moles divided by liters of solution. Use this when you have moles plus a target volume and want the resulting concentration.

Nanomolar to Micromolar Converter

µM = nM / 1000

Convert nanomolar to micromolar — a clean division by 1000 that bridges pharmacology potency work and routine enzyme assays. Formula, worked examples, and a common-values table.

Nanomolar to Millimolar Converter

mM = nM × 10⁻⁶

Convert nanomolar to millimolar by dividing by 10⁶. The factor of a million between trace pharmacology values and the mM concentrations buffers and substrates run at.

Nanomolar to Molar Converter

M = nM × 10⁻⁹

Convert nanomolar to molar by dividing by 10⁹. The step that moves a pharmacology or biochemistry number back into the units used for stock solutions and Beer-Lambert work.

Nanomolar to Picomolar Converter

pM = nM × 1000

Convert nM to pM by multiplying by 1000. The decimal step bridging mid-stage drug-candidate IC50 values and the picomolar Kd of fully optimized binders.

ng/g to PPB Converter

ppb = ng/g × 1

Convert ng/g to ppb. The two units are numerically identical for mass per mass measurements — the conversion is the bookkeeping step between analytical lab output and regulatory reporting.

ng/mL to µg/L Converter

µg/L = ng/mL × 1 (numerically identical)

Convert ng/mL to µg/L — numerically identical units. The 1000-fold scale-up in mass cancels the 1000-fold scale-up in volume.

Normality to Molarity Converter

M = N ÷ n (where n depends on the substance and reaction)

Convert normality to molarity by dividing by the equivalence factor n. The reverse direction of the acid-base or redox scaling that normality was built around.

Osmolarity to Milliosmolarity Converter

mOsm/L = Osm/L × 1000

Convert Osm/L to mOsm/L by multiplying by 1000. The milli prefix step bridging the formal SI unit and the clinical mOsm/L convention.

Parts per Billion to Percent Converter

% = ppb × 10⁻⁷

Convert ppb to percent by multiplying by 10⁻⁷. Seven prefix decades sit between trace-impurity reports and bulk-purity specifications.

Parts per Trillion to PPB Converter

ppb = ppt × 0.001

Convert ppt to ppb by dividing by 1000. The decimal step bridging modern PFAS measurements and pre-2020 trace-contaminant literature.

Parts per Trillion to PPM Converter

ppm = ppt × 10⁻⁶

Convert ppt to ppm by multiplying by 10⁻⁶. The six-decade gap separating semiconductor-grade ultrapure water and bulk industrial-process specifications.

Percent to mg/kg Converter

mg/kg = % × 10000

Multiply by 10,000. Same physical quantity (parts by mass), different scale — percent for bulk material grading, mg/kg for trace-contaminant work.

Percent to mg/L Converter

mg/L = % × 10000

Multiply by 10,000. The factor is exact for dilute aqueous solutions; for anything denser than water you need an explicit density correction.

Percent to Parts per Billion Converter

ppb = % × 10⁷

Convert percent to ppb by multiplying by 10⁷. The factor that takes a bulk-purity percentage into the ppb scale used for trace-impurity specification on a certificate of analysis.

Percent to PPM Converter

ppm = % × 10000

Convert percent to parts per million by multiplying by 10,000. The scale-up step between bulk composition and trace-contaminant notation.

Percent v/v to mL/L Converter

mL/L = % v/v × 10

Convert % v/v to mL/L by multiplying by 10. Needed when percent volume composition crosses into the mL/L form a bench-prep dilution calculation expect.

Percent w/v to g/100mL Converter

g/100mL = % w/v × 1

Convert % w/v to g/100 mL. The two notations describe the same quantity by definition — % w/v is grams of solute per 100 mL of solution.

Percent w/v to g/L Converter

g/L = % w/v × 10

Convert % w/v to g/L by multiplying by 10. The simple ten-fold step between the percent notation on a clinical or pharma label and the g/L units used in lab calculations.

Percent w/v to mg/mL Converter

mg/mL = % w/v × 10

Convert % w/v to mg/mL by multiplying by 10. The clean factor that takes a clinical or pharma label concentration into the mg/mL units a dose calculation actually uses.

Percent w/v to PPM Converter

ppm = % w/v × 10000

Convert % w/v to ppm by multiplying by 10,000. The factor that takes a clinical or pharma label concentration into the ppm scale environmental and water-quality reports use.

Percent w/w to PPM Converter

ppm = % w/w × 10000

Convert % w/w to ppm by multiplying by 10,000. A unit step between bulk weight-percent specifications and ppm-scale impurity reporting.

Picomolar to Micromolar Converter

µM = pM × 10⁻⁶

Convert picomolar to micromolar — the conversion you run when a tight binding constant in pM has to be compared against a micromolar working concentration. Formula, worked examples, and a values table.

Picomolar to Millimolar Converter

mM = pM × 10⁻⁹

Convert pM to mM by multiplying by 10⁻⁹. Nine prefix decades sit between ultra-high binding constants and bench-scale buffer concentrations.

Picomolar to Molar Converter

M = pM × 10⁻¹²

Convert pM to M by multiplying by 10⁻¹². Twelve prefix decades sit between trace-binding constants and bench-stock molarity.

Picomolar to Nanomolar Converter

nM = pM × 0.001

Convert picomolar to nanomolar by dividing by 1000. The step up the concentration ladder you make when comparing a tight binding constant in pM against a working dose in nM.

PPB (Air) to µg/m³ Converter

µg/m³ = (ppb × MW) ÷ 24.45

µg/m³ = (ppb × MW) / 24.45. The molecular weight has to be in there because ppb in air is a mole ratio while µg/m³ is mass per volume — and 24.45 is the ideal-gas molar volume at 25 °C and 1 atm.

PPB to mg/L Converter

mg/L = ppb ÷ 1000

Convert ppb to mg/L by dividing by 1000. For dilute aqueous solutions the equivalence is exact: 1000 ppb = 1 mg/L = 1 ppm.

PPB to ng/g Converter

ng/g = ppb × 1 (numerically identical)

Convert ppb to ng/g — numerically identical for any mass per mass ratio. The two notations describe the same trace concentration with different prefix labels.

PPB to Parts per Trillion Converter

ppt = ppb × 1000

Convert ppb to ppt by multiplying by 1000. The decimal step bridging historical ppb-scale environmental data and modern ppt-scale PFAS measurements.

PPB to PPM Converter

ppm = ppb ÷ 1000

Convert ppb to ppm by dividing by 1000. The decimal step bridging trace water-quality measurements and bulk soil-contamination data.

PPB to µg/kg Converter

µg/kg = ppb × 1 (numerically identical)

Convert ppb to µg/kg — numerically identical for any mass per mass ratio. Both notations describe the same trace concentration with different prefix labels.

PPB to µg/L Converter

µg/L = ppb × 1 (for dilute aqueous solutions)

For dilute aqueous samples, ppb and µg/L are the same number — 1 ppb of solute in water works out to 1 µg per liter. The identity only holds when the matrix density is close to 1 g/mL.

PPM (Air) to mg/m³ Converter

mg/m³ = (ppm × MW) ÷ 24.45

Convert ppm in air to mg/m³ via mg/m³ = (ppm × MW) / 24.45. Comes up at the boundary of mole-ratio exposure limits and mass-concentration analytical readings.

PPM (v/v) to µL/mL Converter

µL/mL = ppm (v/v) ÷ 1000

Convert ppm v/v to µL/mL by dividing by 1000. The decimal step bridging stack-emissions monitoring and laboratory dilution-calibration calculations.

PPM to g/kg Converter

g/kg = ppm ÷ 1000

Convert ppm to g/kg by dividing by 1000. The decimal step bridging trace analytical results and bulk supplement formulation in soil and feed work.

PPM to g/L Converter

g/L = ppm ÷ 1000

Convert ppm to g/L by dividing by 1000. For dilute aqueous solutions the equivalence is exact: 1000 ppm = 1 g/L.

PPM to mg/kg Converter

mg/kg = ppm × 1 (numerically identical)

Convert ppm to mg/kg — numerically identical for any mass per mass ratio. The two notations describe the same trace concentration with different prefix labels.

PPM to mg/L Converter

mg/L = ppm × 1 (for dilute aqueous solutions)

Convert ppm to mg/L — a 1:1 equivalence for dilute aqueous solutions. The identity that holds as long as your solvent is close to water in density.

PPM to Molarity Converter

M = (ppm ÷ 1000) ÷ MW (for aqueous solutions)

Convert ppm to molarity via M = (ppm/1000) / MW. Comes up at the boundary of regulatory mass-concentration data into the molar form geochemical speciation needs.

PPM to Parts per Trillion Converter

ppt = ppm × 10⁶

Convert ppm to ppt by multiplying by 10⁶. Six prefix decades sit between industrial-process water and semiconductor-grade ultrapure water.

PPM to Percent Converter

% = ppm ÷ 10000

Convert ppm to percent by dividing by 10,000. Used when trace concentrations must meet the percent-scale form bulk specifications expect.

PPM to Percent w/v Converter

% w/v = ppm ÷ 10000

Divide by 10,000. The factor is exact for dilute aqueous solutions — strictly speaking it relies on density being 1 g/mL, which is fine for water-quality work and breaks for anything you'd call concentrated.

PPM to Percent w/w Converter

% w/w = ppm ÷ 10000

Convert ppm to % w/w by dividing by 10,000. Used when trace-impurity ppm-scale specs must meet the bulk-purity percent-scale form total-impurity tables expect.

PPM to PPB Converter

ppb = ppm × 1000

Convert ppm to ppb by multiplying by 1000. The decimal step bridging soil-matrix contaminant concentrations and drinking-water trace measurements.

µg/kg to PPB Converter

ppb = µg/kg × 1 (numerically identical)

µg/kg and ppb are the same number for any mass-per-mass ratio. Different labels for the same trace concentration.

µg/L to Grams per Liter Converter

g/L = µg/L × 10⁻⁶

Convert µg/L to g/L by multiplying by 10⁻⁶. A jump of six prefix decades, the gap between trace drinking-water analysis and bulk-brine source-water characterization.

µg/L to mg/L Converter

mg/L = µg/L × 0.001

Convert µg/L to mg/L by dividing by 1000. The decimal step bridging trace polishing-effluent measurements and the mg/L form NPDES permits use.

µg/L to ng/mL Converter

ng/mL = µg/L × 1 (numerically identical)

Convert µg/L to ng/mL — numerically identical for any aqueous solution. The two notations describe the same trace concentration with different prefix combinations.

µg/L to PPB Converter

ppb = µg/L × 1 (for dilute aqueous solutions)

For dilute aqueous samples, µg/L and ppb are the same number — the conversion is the paper-trail step between an ICP-MS output and a public-facing compliance report.

µg/m³ to PPB (Air) Converter

ppb = (µg/m³ × 24.45) ÷ MW

ppb = (µg/m³ × 24.45) ÷ MW. The 24.45 is the ideal-gas molar volume at 25 °C and 1 atm; the molar mass is in there because µg/m³ is mass per volume while ppb in air is a mole ratio.

µg/mL to mg/L Converter

mg/L = µg/mL × 1 (numerically identical)

Convert µg/mL to mg/L — numerically identical for any aqueous solution. Both notations describe the same concentration with different prefix combinations.

µL/mL to PPM (v/v) Converter

ppm (v/v) = µL/mL × 1000

Convert µL/mL to ppm v/v by multiplying by 1000. The decimal step bridging gas-dilution calibration math and stack-monitor instrument output.

Frequently Asked Questions

What is the difference between molarity and molality?
Molarity (M) is moles of solute per liter of solution, while molality (m) is moles of solute per kilogram of solvent. Molarity depends on temperature (because volume changes with temperature), while molality does not. For dilute aqueous solutions at room temperature, the values are nearly identical.
How do I convert between M, mM, µM, and nM?
These are metric prefixes applied to moles per liter. 1 M = 1000 mM = 1,000,000 µM = 1,000,000,000 nM. To go from a larger unit to a smaller one, multiply by 1000 per step. To go the other direction, divide by 1000 per step.
Why are concentration units important in biochemistry?
Biological processes operate at very low concentrations. Enzyme kinetics, drug-receptor binding, and signaling molecules work in the micromolar to nanomolar range. Using the wrong prefix can mean the difference between a therapeutic dose and a toxic one, or between an active enzyme and an inhibited one.