When a label says “1:4,” it almost always counts parts: 1 part concentrate and 4 parts water. The fraction of concentrate comes from comparing that one part with all 5 parts, which is why the denominator is 5. The confusion arises because “1:4” and “1/4” look alike, and because some notations compare with the total instead of with the water.
| On the label | What it counts | Concentrate | Water |
|---|---|---|---|
| 1:4 (concentrate : water) | 1 + 4 = 5 parts | 1/5, or 20% | 4/5 |
| 1:3 (concentrate : water) | 1 + 3 = 4 parts | 1/4, or 25% | 3/4 |
| "1 in 4" or "1 out of every 4" | 1 part within a total of 4 | 1/4, or 25% | 3/4 |
The second and third rows give the same result in different words: a “1 in 4” mix is the same as a 1:3 ratio. What changes between rows is the number of parts, never the rule.
Why a 1:4 ratio has five parts
A ratio compares two quantities of the same kind. In 1:4, the concentrate is compared with the water, not with the finished mix. To get a fraction of the total you have to add first: 1 + 4 = 5, and the concentrate is 1 of those 5 parts. Omni Calculator describes it the same way for another case: in a 1:3 ratio you add 1 unit of concentrate to 3 of water and end up with 4 units in total.
The other reading exists too. English Wikipedia’s article on dilution ratios describes a dilution factor of one fifth as combining 1 unit of solute with about 4 units of solvent to give 5 units in total, so there the number compares with the total, not with the solvent. When you see a slash or a colon with no other text, check whether the big number is the amount of water or the amount of the whole.
The same calculation works for any 1:N ratio. The mix has N + 1 parts and the concentrate is 1/(N + 1). The ratio to fraction converter does that addition for you and returns the fraction in lowest terms. The guide to ratio, proportion and fraction explains why a part-to-part ratio and a part-to-whole fraction cannot be swapped without adding.
How much concentrate and water for 1 L
Worked example: 1 liter at a 1:4 ratio
You want to make 1 liter of mix at a 1:4 dilution, meaning 1 part concentrate and 4 parts water. How many milliliters of each do you need?
- Convert the liter to milliliters. 1 L = 1,000 mL.
- Add the parts. 1 + 4 = 5.
- Work out the concentrate. 1000 × 1/5 = 200 mL.
- Work out the water. 1000 × 4/5 = 800 mL.
Result: 200 mL of concentrate and 800 mL of water.
Check: 200 + 800 = 1000 mL, and the water is 4 times the concentrate because 800 = 4 × 200.
Other volumes follow the same procedure. The table gathers the most common ones; in every row the water is four times the concentrate.
| Final mix | Concentrate | Water |
|---|---|---|
| 500 mL | 100 mL | 400 mL |
| 750 mL | 150 mL | 600 mL |
| 2 L | 400 mL | 1.6 L |
| 5 L | 1 L | 4 L |
For other volumes, the fraction of a number tool multiplies the total by the concentrate fraction and by the water fraction.
If you already know how much concentrate you have
The reverse is a division. With 300 mL of concentrate, the full mix is 300 ÷ 1/5 = 1500 mL, which is 300 × 5, and the water you add is 1500 − 300 = 1200 mL. Set up as a proportion, 1/5 = 300/1500 checks out with cross products: 1 × 1500 and 5 × 300 are equal. The proportions calculator solves for whichever term is missing.
The percentage in a 1:4 dilution
A percent is a fraction written over 100, so 1/5 equals 20/100 and the mix is 20% concentrate. To turn any concentrate fraction into a percent, use fraction to percent, and for the reverse, percentages. The 25% in the table above belongs to a different mix, the 1:3, not the 1:4.
When the label says something else
The arithmetic on this page assumes the second number in the ratio is the water. If the container makes clear that the second number is the total volume of the mix, the concentrate is 1/4 of the volume and is worked out like the last row of the first table. The manufacturer’s instructions always come first, and this page does not cover safe use, product compatibility, or the difference between measuring by volume and by weight.
“1:4” has another meaning that has nothing to do with mixes: on a 1:4 scale, the measurements in the drawing are one quarter of the real ones. To compare two containers with different concentrations, the unit price guide shows which one goes further.
Practice
Three mixes to work out
- You need 900 mL at a 1:2 ratio. How much concentrate and how much water?
- You are making 500 mL at a 1:9 ratio. How much concentrate?
- You have 120 mL of concentrate and the label asks for 1:4. How much mix do you get in total?
Show the answers
- 300 mL of concentrate and 600 mL of water, because there are 3 parts and 900 ÷ 3 = 300.
- 50 mL, because there are 10 parts and 500 ÷ 10 = 50. The water is 450 mL.
- 600 mL, because 120 × 5 = 600; the water is 480 mL.
Sources
- Omni Calculator, Dilution ratio calculator: a 1:3 ratio gives a total of 4 units of volume, and a 1:4 ratio is 1 part concentrate plus 4 parts water, 5 parts in total (accessed October 17, 2026).
- Wikipedia, Dilution ratio: a 1:5 ratio combines 1 unit of solute with 5 units of solvent for 6 in total, while a dilution factor of 1/5 combines 1 unit of solute with about 4 units of solvent for 5 in total (accessed October 17, 2026).