Dilution Calculator

How to use the dilution calculator

1. Enter any three of the four values - stock concentration, stock volume, final concentration, final volume.
2. Pick the unit next to each value; mixed units like mM with µL are fine.
3. Leave the value you want blank. It solves itself and is highlighted, scaled to a readable unit.
4. Fill all four to check an existing dilution instead: you get Balanced or the percentage it is off.
5. For a ratio such as 1:200, switch to 1:N, enter N and the final volume, and read the stock and diluent volumes.

Worked example

What volume of a 10 mM stock makes 20 mL of a 50 µM solution? V₁ = (50 µM × 20 mL) ÷ 10 mM = 0.1 mL, shown as 100 µL - the amount of stock to pipette before topping up to 20 mL.

Dilution factor and ratio

The dilution factor is C₁ ÷ C₂: how many times weaker the working solution is than the stock. A factor of 200× is written as the ratio 1 : 200 - 1 part stock in 200 parts total, i.e. 1 part stock plus 199 parts diluent.

1:N dilutions

Use 1:N when you have a ratio and a final volume but no stock concentration. A 1:200 dilution is 1 part stock in 200 parts of the finished solution. For 1 mL that is 1 ÷ 200 = 5 µL of stock and 995 µL of diluent. A 1:400 dilution into the same 1 mL is 2.5 µL of stock and 997.5 µL of diluent. Antibody preparations use this same split: the stock volume is the antibody, and the diluent is the buffer.

What it is for

Reagents are stored concentrated and used dilute. This calculator turns a storage stock into a working solution: antibiotics, buffers, antibodies, standards - anywhere the equation C₁V₁ = C₂V₂ applies. For weighing out a solid from scratch, use the Molarity Calculator instead. For the 1:10 / 1:100 / 1:200 conventions and serial-dilution math, see the guide Understanding 1:10, 1:100, and 1:200 dilutions.