Ratio Calculator
This ratio calculator covers the three jobs a ratio actually does: reduce A:B to its smallest whole numbers, solve a proportion like 4:6 = 10:x, and split a total volume by a dilution ratio like 1:10. Decimals such as 2.5:1.5 are handled without rounding tricks.
Simplified ratio
2:3
4:6 = 2:3
Examples
How to use
- 1
Pick a mode: simplify a ratio, solve a proportion or split a dilution.
- 2
Type the two sides of your ratio, decimals like 2.5 work too.
- 3
For proportions and dilutions, add the third value or the total volume.
- 4
Read the result instantly, then copy or download it with the buttons under the tool.
What is a ratio and how does the tool read it?
A ratio compares two quantities: 4:6 means 4 parts of one thing for 6 parts of another. Two ratios are equivalent when one is a multiple of the other, so 4:6, 2:3 and 200:300 all describe the same mix. The calculator always reasons in exact whole parts. Type decimals and it first scales both sides by the same power of ten (2.5:1.5 becomes 25:15), then reduces.
Simplifying a ratio
Simplifying divides both sides by their greatest common divisor. For 4:6 the GCD is 2, so the reduced form is 2:3. For a screen resolution like 1920:1080 the GCD is 120, which gives the familiar 16:9. Reduced ratios are easier to compare, scale and remember.
Solving a proportion A:B = C:x
The solve mode finds the missing fourth value by cross multiplication: x = B × C ÷ A. If a recipe uses 4 cups of flour for 6 cups of water and you scale the flour to 10 cups, the water becomes x = 6 × 10 ÷ 4 = 15 cups. The same one-line formula settles map scales, currency conversions and paint mixes.
Dilution ratios and total volume
Cleaning products, garden concentrates and lab solutions carry dilution ratios like 1:10, one part product for 10 parts water. The dilution mode splits your total volume in those proportions: product = total × 1 ÷ 11 and water = total × 10 ÷ 11. For a 550 ml spray bottle at 1:10, that gives exactly 50 ml of product and 500 ml of water.
What do worked examples look like?
| Task | Input | Result |
|---|---|---|
| Reduce a ratio | 4:6 | 2:3 |
| Reduce with decimals | 2.5:1.5 | 5:3 |
| Solve a proportion | 4:6 = 10:x | x = 15 |
| Dilute at 1:10 | 550 ml total | 50 ml product + 500 ml water |
Where do ratios show up?
Beyond cleaning products, the same three modes cover aspect ratios (a 1920 by 1080 video is 16:9, so a 1280 pixel wide export needs 1280 × 9 ÷ 16 = 720 pixels of height), baking (a 5:3 flour to butter shortbread scaled to 500 g of flour needs 300 g of butter), two-stroke fuel mixes at 50:1, and mortar or concrete blends like 1:2:3 handled two parts at a time.
What units and limits apply?
The calculator is unit-agnostic: as long as both sides of a ratio share the same unit, the result holds in milliliters, liters, cups or ounces. Ratio parts take values from 0.0001 up to one billion. The proportion and dilution modes need a third value above zero; everything else, the missing value x included, is computed at full precision and rounded only for display.
Parameters
Every field of this tool can be prefilled from the URL. Use these query parameters:
| Parameter | Type | Default |
|---|---|---|
| mode | simplify | solve | dilution | simplify |
| a | number | 4 |
| b | number | 6 |
| c | number | 10 |
Example : https://www.veltotools.com/math/ratio-calculator?mode=simplify&a=4&b=6
API
The same tool is available as a free JSON API, with the same parameters as above. No key, no sign-up.
Frequently asked questions
Updated Jul 21, 2026