How It Works
This converter works in 4 steps.
Enter the molarity
Type the value in M, mM, µM, or nM.
Enter the molecular weight
Type the MW from the label, including salt and hydrate forms.
Enter a volume (optional)
Type a volume to get the grams to weigh.
Read the results
The converter returns g/L, mg/mL, % w/v, and mass for the stated volume.
The Formula
The formula multiplies molarity by molecular weight.
ρ (g/L) = M × MWM = ρ / MWm (g) = M × MW × V (L)- M:
- Molarity (mol/L)
- MW:
- Molecular weight (g/mol)
- ρ:
- Mass concentration (g/L)
- V:
- Solution volume (L)
1 M Tris base (MW 121.14 g/mol) equals 121.14 g/L. One liter needs 121.14 g; 250 mL needs 30.29 g.
Conversion Table
The conversion table converts 6 common lab reagents from mM to g/L and % w/v.
| Reagent | MW | Molarity | Mass concentration | % w/v |
|---|---|---|---|---|
| NaCl | 58.44 g/mol | 150 mM | 8.766 g/L | 0.8766% w/v |
| Glucose | 180.2 g/mol | 5 mM | 0.9008 g/L | 0.09008% w/v |
| Tris base | 121.1 g/mol | 1,000 mM | 121.1 g/L | 12.11% w/v |
| EDTA disodium dihydrate | 372.2 g/mol | 500 mM | 186.1 g/L | 18.61% w/v |
| ATP disodium | 551.1 g/mol | 100 mM | 55.11 g/L | 5.511% w/v |
| BSA | 66,430 g/mol | 0.015 mM | 0.9965 g/L | 0.09965% w/v |
What Is the Molarity-to-Mass Concentration Converter?
The Molarity-to-Mass Concentration Converter is a tool that converts molar concentration into mass concentration, and back, using the molecular weight (MW) of the solute in g/mol. Mass concentration in g/L equals molarity in mol/L multiplied by MW.
The correct MW includes any salt form or water of hydration listed on the label. EDTA disodium dihydrate has an MW of 372.24 g/mol, not the 292.24 g/mol of free EDTA. The converter takes the MW the user enters and returns g/L, mg/mL, % w/v, and the grams needed for a chosen volume.
Common Uses
There are 5 main uses of this converter.
Buffer recipes
Users weigh Tris, HEPES, and salts for molar buffer recipes.
Protein molarity
Biochemists convert mg/mL protein readings into µM using the protein MW.
Drug solutions
Pharmacologists convert mg/mL drug stocks into mM.
Label checks
Technicians confirm a supplier's mg/mL against a molar spec.
Literature conversion
Researchers convert published µg/mL values into µM.