Molarity from Mass & Volume

Calculating Concentration from Mass and Volume

When to Use This Calculator

This tool combines the standard molarity formula and complex unit conversions into a single step. Use this if you weighed out a certain amount of chemical powder, added a specific volume of solvent, and now need to know the exact concentration of the resulting solution.

How It Works

Instead of manually converting your mass to grams and your volume to Liters, this advanced calculator allows you to input the exact units you used in the lab (like milligrams and microliters). It converts the mass to moles, and then divides it by the total volume to give you your final molarity.

The Concentration Formula

The standard equation behind the calculation is:

Step-by-step Example

Imagine you dissolve 5.84 grams of NaCl (Table Salt, Formula Weight = 58.44 g/mol) into enough water to make exactly 500 mL (0.5 L) of solution.

1. First, find the moles: 5.84 g / 58.44 g/mol = 0.1 moles.
2. Next, calculate the concentration: 0.1 moles / 0.5 L = 0.2 M.
3. Finally, convert to a workable unit: 0.2 Molarity equals exactly 200 millimolar (mM).

Common Mistakes

• Disregarding Solvent Displacement: When adding solvent to a dry powder, the powder itself takes up a tiny amount of volume. For exact molarity, you should dissolve the mass in less than your target volume, and then "top it up" to the final volume line using a volumetric flask.