Volume from Mass & Concentration

Determining Final Volume from Known Mass and Concentration

When to Use This Tool

This calculator is perfect for situations where you have pre-weighed a specific amount of compound (such as a vial of lyophilized peptide or a pre-packaged reagent) and need to reconstitute it to a specific molarity. It tells you exactly how much solvent to add to achieve your target concentration.

How the Calculator Works

Our tool reverses the standard molarity equation. By entering the mass of your compound, its formula weight (molar mass), and the target concentration you want to achieve, it instantly computes the total required volume in microliters, milliliters, or liters.

The Reconstitution Formula

To find the necessary volume, you convert the mass to moles, and then divide by the desired molarity:

Step-by-step Example

Imagine you have exactly 180 mg (0.180 g) of a chemical with a formula weight of 180.16 g/mol, and you want to create a 0.1 M (100 mM) solution.

1. First, convert the mass to moles: 0.180 g / 180.16 g/mol = 0.001 moles.
2. Next, divide the moles by your target molarity: 0.001 moles / 0.1 mol/L = 0.010 L.
3. Finally, convert liters to a workable unit: 0.010 Liters is exactly 10 milliliters (mL).

Common Mistakes

• Disregarding Solvent Displacement: When adding solvent to a dry powder, the powder itself takes up a tiny amount of volume. For highly precise work, you add solvent until the total mixture reaches the target volume, rather than just dumping in the exact calculated volume of solvent.