Percent Dilution Calculator
Use this calculator to determine how much stock solution and how much diluent (usually water or buffer) you need to prepare a target percentage solution.
After Adding Solvent: New Percent
Optional quick tool: find new concentration after adding diluent to an existing solution.
What is a percent dilution calculator?
A percent dilution calculator helps you prepare weaker solutions from stronger stock solutions. Instead of doing the math manually every time, you enter concentration and volume values, and the calculator gives you the exact mixing amounts.
This is useful in labs, cleaning protocols, home chemistry, cosmetics, brewing, and food preparation. The most common use case is: “I have a high concentration stock solution. How much do I use to make a lower concentration final solution?”
The core formula: C1V1 = C2V2
The calculator uses the classic dilution equation:
C1 × V1 = C2 × V2
- C1 = stock concentration (%)
- V1 = stock volume required
- C2 = target concentration (%)
- V2 = final total volume
Rearranging gives: V1 = (C2 × V2) / C1
Once you know V1, the amount of diluent is: V2 - V1
Important rule
You can only dilute to a concentration that is less than or equal to your stock concentration. If your target percent is higher than stock percent, dilution alone cannot do it.
Worked example
Suppose you need 500 mL of 10% solution from a 70% stock.
- C1 = 70
- C2 = 10
- V2 = 500 mL
V1 = (10 × 500) / 70 = 71.43 mL stock
Diluent = 500 - 71.43 = 428.57 mL
So you mix 71.43 mL stock with 428.57 mL diluent.
Percent types matter (v/v, w/v, w/w)
“Percent” can mean different things depending on context:
| Notation | Meaning | Typical Use |
|---|---|---|
| % v/v | mL solute per 100 mL solution | Alcohol mixtures, solvents |
| % w/v | grams solute per 100 mL solution | Biology and chemistry reagents |
| % w/w | grams solute per 100 g solution | Food, formulations, industrial blends |
The formula is still conceptually useful, but you must keep units consistent with the type of percent you are using.
Best practices for accurate dilution
- Use calibrated measuring tools (pipettes, volumetric flasks, graduated cylinders).
- Keep units consistent from start to finish.
- Record concentration basis clearly (% v/v, % w/v, or % w/w).
- Add stock first, then diluent up to the final target volume.
- Mix thoroughly before use.
Frequently asked questions
Can I use this for ppm or molarity?
The same dilution principle applies, but this calculator is designed for percent concentration inputs. For ppm, molarity, or normality, use the corresponding units consistently and a dedicated calculator if needed.
Why does my measured final concentration differ slightly?
Small differences can come from rounding, temperature effects, instrument tolerance, evaporation, or incomplete mixing.
Can I scale any recipe up or down?
Yes. If concentration values stay the same, changing final volume scales stock and diluent volumes proportionally.
Final takeaway
A dilution calculator for percent solutions saves time and reduces mistakes. Enter your stock percent, target percent, and final volume, then use the recommended stock volume and diluent volume to prepare your solution accurately.