Molar to Millimolar Converter

Common Conversions

M	mM
0.0001	0.1
0.001	1
0.005	5
0.01	10
0.05	50
0.1	100
0.25	250
0.5	500
1	1000
2	2000
5	5000

Why this conversion matters in chemistry

Stocks live in molar — a 1 M Tris·HCl, a 5 M NaCl, a 12 M HCl. Working buffers and assay reactions live in millimolar. Diluting a 1 M Tris stock 1:20 into a buffer gives a 50 mM working concentration, the kind of value that anchors a typical wash step or an enzyme reaction. Multiplying by 1000 is the ordinary step that lines up the label on the bottle with the recipe in the protocol. The same arithmetic is what makes a stockroom inventory and a method section talk to each other.

Formula

mM = M × 1000

Worked Examples

1 M = 1000 mM

One molar — the conversion anchor, and a typical Tris-HCl or buffer stock concentration.

0.1 M = 100 mM

A common working buffer concentration for protein chemistry and gel running.

0.01 M = 10 mM

A dilute substrate or chelator working concentration for biochemical assays.

0.001 M = 1 mM

Millimolar-level — the floor of working buffer concentrations before stepping down to µM.

Frequently Asked Questions

How do I convert M to mM?

Multiply by 1000. The relationship is exact, so 0.1 M is precisely 100 mM with no rounding.

Which notation is preferred?

Below 1 M, millimolar usually reads more cleanly — 50 mM instead of 0.05 M. At or above 1 M, the molar notation is standard. The choice mostly comes down to which prefix keeps the digits easy.

Are molarity and molar the same?

Yes. Molarity is the property; molar (M) is the unit. Both mean moles of solute per liter of solution, and both share the symbol mol/L when written out.

What concentrations are common in lab work?

Stock solutions sit at 1–12 M. Working buffers tend to land in 10–100 mM. Enzyme substrates run 0.1–10 mM. Drug-screening dose-response titrations cover 1–100 µM and below. The prefix tracks the scale at each step.