How It Works
This calculator works in 4 steps.
Enter the assay percent
Type % w/w from the bottle or certificate.
Enter the density
Type the specific gravity or density in g/mL.
Enter the molecular weight
Type the MW of the active compound.
Read the molarity
The calculator returns M and the mL of concentrate per liter of 1 M solution.
The Formula
The formula multiplies density, mass percent, and 10, then divides by molecular weight.
M = (10 × ρ × w) / MWV (mL) = 1,000 / M- M:
- Molarity (mol/L)
- ρ:
- Density (g/mL)
- w:
- Assay (% w/w)
- MW:
- Molecular weight (g/mol)
98% sulfuric acid at 1.84 g/mL: M = 10 × 1.84 × 98 / 98.08 = 18.4 M. 1 L of 1 M H₂SO₄ needs 54.4 mL of concentrate.
Conversion Table
The conversion table lists the molarity of 7 common concentrated reagents and the volume per liter of 1 M solution.
| Reagent | Assay | Density | MW | Molarity | mL per 1 L of 1 M |
|---|---|---|---|---|---|
| Hydrochloric acid (HCl) | 37% | 1.19 g/mL | 36.46 g/mol | 12.1 M | 82.8 mL |
| Sulfuric acid (H₂SO₄) | 98% | 1.84 g/mL | 98.08 g/mol | 18.4 M | 54.4 mL |
| Nitric acid (HNO₃) | 70% | 1.42 g/mL | 63.01 g/mol | 15.8 M | 63.4 mL |
| Acetic acid, glacial | 99.7% | 1.05 g/mL | 60.05 g/mol | 17.4 M | 57.4 mL |
| Phosphoric acid (H₃PO₄) | 85% | 1.69 g/mL | 98 g/mol | 14.7 M | 68.2 mL |
| Ammonium hydroxide (as NH₃) | 28% | 0.9 g/mL | 17.03 g/mol | 14.8 M | 67.6 mL |
| Hydrogen peroxide (H₂O₂) | 30% | 1.11 g/mL | 34.01 g/mol | 9.79 M | 102 mL |
Values use typical label assay and density at 20 °C (68 °F). Check the lot certificate for exact figures.
What Is the Concentrated Reagent Molarity Calculator?
The Concentrated Reagent Molarity Calculator is a tool that returns the molarity of a concentrated liquid reagent from its assay percent (% w/w), density, and molecular weight. 37% hydrochloric acid with a density of 1.19 g/mL is 12.1 M.
Bottles of concentrated acids and bases list % w/w and density, not molarity. The molarity is the starting value for every dilution of that reagent. The calculator returns M and the volume of concentrate needed per liter of 1 M solution.
Common Uses
There are 5 main uses of this calculator.
Acid dilution planning
Chemists compute V₁ for 1 M and 0.1 M acids.
Titrant preparation
Analysts prepare standard acids before standardization.
Sample digestion
Labs prepare nitric and hydrochloric acid digestion mixes.
Lot checks
QC staff compare lots with different assay values.
Teaching
Instructors show the link between % w/w, density, and M.