Dilution Calculator (C1V1 = C2V2): How Much Stock and Water to Mix
Choose what to find, enter the strengths and volumes you know, and see how much stock and how much water to use.
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Stock to take
353.54ml
- Water or solvent to add
- 146.46 ml
- Final volume
- 500 ml
- Dilution
- 1 : 1.414
Use the same unit for C1 and C2 (%, mol/L or mg/L).
Show working
- C1 × V1 = C2 × V2
- 99 × 353.535 = 70 × 500
How to use
- Choose what to find: stock volume, final volume or final concentration.
- Enter the stock strength C1 and the other known values. Use the same unit for C1 and C2.
- Measure the stock, then add water (or solvent) up to the final volume.
Good to know
C1 × V1 = C2 × V2: the amount of solute stays the same when you add water. To make 500 ml of 70% alcohol from 99% stock: V1 = 70 × 500 ÷ 99 = 353.5 ml of stock, made up to 500 ml with about 146.5 ml of water.
Concentrations can be in any unit — %, mol/L, mg/L, or ‘parts’ — as long as C1 and C2 use the same unit. Volumes come out in the same unit you put in. Dilution factor = V2 ÷ V1.
Some liquids shrink when mixed: alcohol and water together give slightly less than the sum of the two volumes. For accurate work, add the stock to a measuring flask and top up with water to the final mark rather than adding a fixed volume of water. For household chemicals, follow the label.
Questions
What does C1V1 = C2V2 mean?
Starting concentration × starting volume = final concentration × final volume. The amount of solute does not change.
Can I make a stronger solution by dilution?
No. C2 must be lower than or equal to C1. Dilution only makes solutions weaker.
What units should I use?
Any, as long as C1 and C2 match (both %, both mol/L) and V1 and V2 match.
How do I make 70% alcohol from 99%?
Take 353.5 ml of 99% and add water up to 500 ml. For 1 litre, take 707 ml.
Is this suitable for medicines?
No. Do not use it to prepare medicines or doses. Follow your doctor or pharmacist.