Dilution Calculator
Solve C1V1 = C2V2 for any variable: pick what to find, enter the three values you know (the solved-for field is ignored) in any consistent units, and see how much water to add.
Example: with Solve for Stock volume needed (V1) · Stock concentration (C1) 10 · Stock volume (V1) 50 · Final concentration (C2) 1 · Final total volume (V2) 500 → Solved value: V1 = 50.00.
Computed by the calculator below using its default values. Change any input to see your own numbers.
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Check it outC1V1 = C2V2 — and how much water to actually add
A dilution keeps the amount of dissolved stuff constant while the volume grows, so C1 × V1 = C2 × V2. To make 500 mL of a 1 M solution from a 10 M stock: V1 = (1 × 500) ÷ 10 = 50 mL of stock. The part people get wrong is the water: you add V2 − V1 = 450 mL, topping up to 500 mL total — you do not add 500 mL. The equation works in any consistent units: M or %, mL or ounces.
Dilution ratios like 1:32 on cleaning labels
Lab notation usually treats 1:32 as a 32× dilution factor — 1 part stock in 32 parts total. Most cleaning-product labels mean 1 part concentrate plus 32 parts water instead. The everyday shortcut still works: for a 1:32 label, 128 ÷ 32 = 4 oz of concentrate per gallon of water. For a 1:10 mop-bucket mix, 12.8 oz per gallon. When precision matters, check which convention your label uses — the two differ by one part.
How it’s calculated
Dilution equation: C1 × V1 = C2 × V2, rearranged for whichever variable you pick (for example V1 = C2 × V2 ÷ C1). Water to add = V2 − V1, since you top the measured stock up to the final volume. Dilution factor = V2 ÷ V1 = C1 ÷ C2, shown as 1:DF from stock to final volume. Any units work as long as both concentrations match and both volumes match.
Results update as you type and are estimates, not professional advice — verify important decisions with a qualified professional.
Common mistakes
- Adding V2 of water instead of topping up to V2 — you add V2 − V1 (450 mL in the example, not 500).
- Mixing units — mL against L, or % against M; the equation only works when like quantities share units.
- Pouring water into concentrated acid — always add acid to water slowly, never the reverse.
- Reading 1:32 on a cleaning label as 32× total — many labels mean 1 part product plus 32 parts water (33 parts total).
Frequently asked questions
How do I calculate a dilution?
Use C1V1 = C2V2. To get 250 mL of 0.5 M from a 2 M stock: V1 = (0.5 × 250) ÷ 2 = 62.5 mL of stock, then add water up to 250 mL (187.5 mL of water).
How much water do I add for a 1 to 10 dilution?
In lab convention, 1:10 means a 10× factor: 1 part stock plus 9 parts water — 10 mL of stock plus 90 mL of water gives 100 mL. On cleaning labels, 1:10 often means 1 part product plus 10 parts water.
What does a 1:200 dilution mean?
One part stock in 200 parts total volume. For example, 5 mL of stock topped up to 1,000 mL gives a 200× dilution, because 1,000 ÷ 5 = 200.
How many ounces per gallon is a 1:32 ratio?
A US gallon is 128 fl oz, so 128 ÷ 32 = 4 oz of concentrate per gallon of water — the standard all-purpose-cleaner strength.
Does this work for molarity?
Yes. With molar concentrations it is the familiar M1V1 = M2V2 — the same conservation of moles, in any volume unit you keep consistent.