C1V1 = C2V2 · Ratio

Dilution calculator: C1V1 = C2V2 and 1:X ratios

Mix the working solution right the first time, not the second.

Last updated 2026-09-27. Math runs in your browser, no data leaves your computer.

Use C1V1 = C2V2 when the concentrations are known numbers, and the ratio method when the label or data sheet gives a mix ratio such as 1:10. Both return the stock and water volumes for the batch you want.

Switching the method keeps your volume unit, so you can check a label ratio against a known concentration.

Every volume box below uses this unit, and the result also shows the smaller unit for measuring out.

Fill any three boxes and leave the fourth blank for the tool to solve. The two concentrations can be in any unit, percent, g/L, or ppm, as long as both use the same one.

Take it from the product label or the COA for the lot, since a drum sold as 25 percent can test a point either side.

Usually the unknown, because this is how much concentrate goes into the tank before the water.

The strength your process or procedure calls for, in the same unit as C1, and it has to be lower than C1.

The total batch after the water goes in, which is the working level of the tank or bucket you are filling.

Before the booking, screen the name on the invoice. Shipment pre-check is on the paid plans, from USD 59 a month.

General guidance only. Verify against the cited primary sources before you commit to a shipment, declaration, or contract.

How the two methods work

A dilution moves the same amount of chemical into a larger volume, so concentration times volume stays constant from the drum to the tank. Written out, that is C1 × V1 = C2 × V2, and any one of the four values follows from the other three. The water to add is simply V2 − V1.

The formula is exact for concentrations measured per unit of volume: g/L, percent w/v, percent v/v, or mol/L. For percent w/w it also assumes the stock and the mix have the same density, which is close enough for dilute mixes near SG 1.000 but drifts for strong acid or caustic, where the concentrate is much heavier than the finished solution.

A ratio is the same arithmetic with the concentrations hidden. Read as 1 part to X parts water, the concentrate is 1 / (X + 1) of the batch; read as 1 part in X parts total, it is 1 / X. The US gallon, the 128 fluid ounces in it, and the 29.5735 mL fluid ounce all come from NIST Handbook 44.

Worked example: a 1:4 label and a 20 gallon tank

The booking. A floor cleaner concentrate says dilute 1:4, and the night crew fills a 20 gallon scrubber tank. They read it as 1 part in 4, so 20 / 4 = 5 gallons of concentrate and 15 gallons of water, which looks fine on paper.

The failure. The data sheet meant 1 part concentrate to 4 parts water, five parts in all, so the right charge is 20 / 5 = 4 gallons. Every tank runs 25 percent over strength, leaves residue on the floor, and burns through the drum a quarter faster than the budget allowed. Either the crew changes the mix, or purchasing changes the order quantity.

The fix. Pick "1 part concentrate to X parts water" in the tool, enter 4 and a 20 gallon batch, and it returns 4 gallons of concentrate and 16 of water. Tape that number to the tank, and the drum lasts as long as the reorder schedule assumed.

Working from a COA in ppm or mg/L rather than a label ratio? The concentration converter turns it into the unit you need for C1 and C2 at /tools/chemicals/concentration-converter.

Need the weight of that concentrate for a freight booking or a reorder? The gallons to pounds calculator converts it with the SG from the SDS at /tools/chemicals/gallons-to-pounds-calculator.

Frequently asked

What is the C1V1 = C2V2 formula?

It says the amount of chemical does not change when you add water, only the volume it sits in. C1 and V1 are the concentration and volume of the stock you pour, C2 and V2 are the concentration and volume of the finished mix. To make 10 gallons at 5 percent from a 25 percent stock, V1 = 5 × 10 / 25 = 2 gallons of stock topped up to 10 gallons.

Does 1:10 mean 1 part in 10 or 1 part to 10?

It depends on who wrote the label, which is why the tool asks. Many cleaning labels mean 1 part concentrate to 10 parts water, 11 parts in total, while many lab protocols mean 1 part in 10 parts total. The two readings differ by 10 percent at 1:10 and by 50 percent at 1:2, so check the technical data sheet or ask the supplier before you mix a large batch.

Can I use C1V1 = C2V2 with percent w/w?

Strictly, the formula holds for concentrations per unit volume, such as g/L, percent w/v, percent v/v, or mol/L. With percent w/w it is exact only when the stock and the finished mix have the same density. For dilute mixes near SG 1.000 the error is small; for strong acid or caustic, convert the stock to g/L first with the concentration converter.

How many fluid ounces are in a gallon?

There are 128 US fluid ounces in a US gallon, and one fluid ounce is 29.5735 mL. Both figures come from the definitions in NIST Handbook 44, where the gallon is 231 cubic inches or 3.785411784 liters. The tool shows small volumes in fluid ounces or mL so a measuring jug can be used directly.

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