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Dilution Ratio Calculator

Mix at a ratio like 4:1, or dilute a stock solution to a target concentration. Enter your numbers and read how much product (or stock) and how much water or other diluent to measure, in the unit you choose.

Product

800 ml

Diluent (water or other)

200 ml

Product is 80 % of the final mix (4 parts out of 5).

Common ratios (product : diluent)

Reading a ratio: here 4:1 means 4 parts of product for 1 part of water (or other diluent), so the product is 4 parts out of 5, or 80 %. Some brands write 1+4, which means 1 part of product plus 4 parts of water: enter 1 and 4. A label that says “1 in 5” means 1 part of product in 5 parts of mix: also enter 1 and 4. Check the order on your own label.

The unit you type is only a label: nothing is converted. Volumes are assumed to add up, and results are rounded to 6 significant digits. This is arithmetic only: follow the label of your product, and do not use it for medicine, chlorine or other hazardous products.

How it works

  1. Choose Mix by ratio if you have a ratio, or Stock to target if you have two concentrations.
  2. Enter the parts of product and of diluent, or the stock and target concentrations, then the final volume you want.
  3. Type the unit you measure in. It is only a label and nothing is converted.
  4. Read how much product or stock and how much diluent to measure, then copy the summary.

What people use it for

  • Thinning paint, stain or primer

    A tin gives a ratio. Find the millilitres of product and of water for the quantity you need today.

  • Concentrates and cordials

    Turn “1 part to 4 parts water” into the exact amounts for a litre jug or a single glass.

  • Dye, ink or a stock solution

    Go from a 10 % stock to a 2 % working solution for a given volume, with the stock and the water to measure.

Questions

What does a ratio like 4:1 mean?
Here a:b means a parts of product for b parts of water or other diluent, so 4:1 is 4 parts of product and 1 part of water: the product is 4 ÷ 5 = 80 % of the final mix. Some brands write 1+4, which is 1 part of product plus 4 parts of water, so enter 1 and 4. A label that says “1 in 5” means 1 part of product in 5 parts of mix, which is again 1 and 4. The order matters: 1:4 and 4:1 are very different mixes, so check it on your label.
What are the formulas?
Mix by ratio: product = final volume × a ÷ (a + b) and diluent = final volume × b ÷ (a + b). For 1000 ml at 4:1 that is 800 ml and 200 ml. Stock to target: the stock volume is target × final volume ÷ stock concentration (C1·V1 = C2·V2) and the diluent is what remains. For a stock of 10, a target of 2 and 1000 ml, measure 200 ml of stock and 800 ml of diluent. Volumes are assumed to add up, and results are rounded to 6 significant digits.
Which units can I use?
Any volume unit, as long as the final volume and the amounts you read back are in that same unit. The page repeats the label you type and never converts between ml, litres and ounces; the volume converter does that. In stock mode, write both concentrations in the same unit, such as % or mg/mL. The page reports an error if the target is above the stock or if the stock is 0 or less, because a solution cannot get stronger by adding diluent.
Can I use it for medicine, bleach or hazardous products?
No. The page only does arithmetic and knows nothing about any product. Follow the label of your product for the ratio, the order of mixing, protective equipment and storage. Do not use it for medicine, chlorine or other hazardous chemicals, where a wrong mix can cause harm.