Femtomoles to Picomoles Converter
Common Conversions
| fmol | pmol |
|---|---|
| 1 | 0.001 |
| 5 | 0.005 |
| 10 | 0.01 |
| 50 | 0.05 |
| 100 | 0.1 |
| 250 | 0.25 |
| 500 | 0.5 |
| 1000 | 1 |
| 5000 | 5 |
| 10000 | 10 |
| 100000 | 100 |
| 1000000 | 1000 |
Why this conversion matters in chemistry
Targeted mass-spec assays — selected-reaction monitoring, parallel-reaction monitoring — get built from femtomole anchor points but consume picomole-scale reagent stocks across a campaign. A typical seven-point standard curve from 1 to 1000 fmol on-column, run in triplicate, uses a few pmol of isotope-labeled internal standard per curve. Tracking the arithmetic between femtomoles and picomoles is what keeps an internal-standard inventory honest and lets a method developer estimate when a precious labeled-peptide stock will run out before the next lot arrives.
Formula
Where the factor comes from
Both prefixes are pure powers of ten fixed by definition — femto is 10⁻¹⁵, pico is 10⁻¹² — so their quotient is 10⁻³ and pmol = fmol ÷ 1000. The 1000 is an integer nobody measured and nobody will revise. Since the 2019 revision of the SI the layer underneath is exact as well: a mole holds exactly 6.02214076 × 10²³ elementary entities, which makes a femtomole exactly 602214076 of them and a picomole a thousand times that. The arithmetic is therefore clean all the way down to the molecule. The femtomole figure you feed into it is not. That number came off a calibration curve, an integrated peak area, or an assumed extinction coefficient, and whatever uncertainty those carried travels through the division untouched.
Precision and significant figures
Dividing by an exact thousand leaves the significant figures where they were: 47 fmol is 0.047 pmol, two figures, and 0.0470 would invent a third. The leading zeros are the hazard here, because they look like resolution and are only placeholders. Few numbers at this scale support more than two or three figures anyway. Near the lower limit of quantitation on a triple quadrupole, acceptance windows are routinely set around the twenty percent level, which puts the third digit well inside the noise. Report 0.05 pmol, keep the unrounded value in the spreadsheet so repeated rounding cannot compound, and let the calibration decide how many digits reach the page.
Worked Examples
The conversion anchor — one picomole equals exactly one thousand femtomoles.
A single femtomole, near the lower quantitation limit of most LC-MS/MS methods running in selected-reaction monitoring mode.
A mid-range standard-curve point, typically loaded for a confident quantitation in a targeted assay.
A typical on-column amount for a low-abundance peptide in a quantitative proteomics workflow.
Common mistakes
On-column femtomoles are not vial concentration
An assay reporting 100 fmol means 100 fmol delivered to the column, which depends on injection volume as much as on what sits in the vial. Convert that to 0.1 pmol and it is still an amount, not a concentration. Double the injection and the femtomole figure doubles while the vial is unchanged, so comparisons across methods have to fix the injection volume first.
Surface losses below the picomole level
At femtomole loadings a meaningful fraction of hydrophobic peptides and dyes ends up on tube walls, pipette tips and vial septa rather than in solution. The picomole number your dilution scheme predicts and the picomole number the detector sees can differ substantially, and the gap widens the longer a dilute working solution sits before injection.
Peptide femtomoles read as protein femtomoles
In bottom-up proteomics the quantified species is a peptide, not the protein it came from. Digestion is rarely complete and only some peptides ionize well, so converting 250 fmol of a surrogate peptide into 0.25 pmol of protein assumes a one-to-one recovery the workflow does not deliver. The unit conversion is exact; the inference sitting on top of it is not.