Ratio Calculator
Simplify a ratio, find the missing number in a proportion or share an amount in a given ratio — with the working and a chart of the parts.
- Simplify
- Missing value
- Share an amount
- Private
Separate 2 to 8 values with a colon. Decimals and fractions are fine: 1.5 : 2 or 1/2 : 3/4.
Leave exactly one box empty — that is the value to find.
Example: share 1,200 in the ratio 2 : 3 : 5.
Step by step
How to work with ratios
Three tasks, one tool.
- 1
Choose the task
Simplify a ratio, find a missing value in a proportion, or share an amount.
- 2
Enter the numbers
Type the ratio with colons, such as 12 : 18 : 30, or fill three of the four boxes of the proportion.
- 3
Read the result
You get the simplified ratio, the missing value or the shares — with steps and a chart.
Ratios for recipes, mixes, maps and money
Exact arithmetic, clear explanations.
Simplify any ratio
Two to eight parts, including decimals and fractions such as 1.5 : 2 or 1/2 : 3/4.
Solve proportions
Leave one of the four boxes in a : b = c : d empty and get the missing value exactly.
Share by ratio
Divide money, ingredients or time in a ratio such as 2 : 3 : 5.
Other forms
See the ratio as 1 : n, as a fraction and as percentages of the whole.
Steps shown
Greatest common divisor, cross-multiplication and the value of one part, written out.
Link to your calculation
Copy a link that reopens the calculator with your numbers filled in — handy for sharing or saving a scenario.
Made for phones
Large fields, the right keyboard for numbers and a layout that fits small screens.
Private by design
Everything is calculated in your browser. Your numbers are not sent to a server.
Ratios and proportions explained
A ratio compares quantities of the same kind: 12 : 18 means 12 of one for every 18 of the other. Ratios are simplified like fractions — divide every part by the greatest common divisor. For 12 : 18 : 30 the divisor is 6, giving 2 : 3 : 5. Ratios with decimals or fractions are first multiplied up to whole numbers: 1.5 : 2 becomes 3 : 4.
A proportion states that two ratios are equal: a : b = c : d. If one of the four values is missing, cross-multiply: a × d = b × c. To scale a recipe that uses 3 cups of flour for 4 servings up to 20 servings, solve 3 : 4 = x : 20, so x = 3 × 20 ÷ 4 = 15 cups.
To share an amount in a ratio, add the parts, divide the amount by that total to get the value of one part, and multiply by each part. Sharing 1,200 in the ratio 2 : 3 : 5 gives 10 parts of 120 each, so the shares are 240, 360 and 600. The order of the parts matters: 2 : 3 is not the same as 3 : 2.
Ratios in everyday life
| Where | Ratio | Meaning |
|---|---|---|
| Screens | 16 : 9 | Width to height |
| Maps | 1 : 50,000 | 1 cm on the map is 500 m on the ground |
| Concrete mix | 1 : 2 : 3 | Cement, sand and gravel by volume |
| Vinaigrette | 3 : 1 | Oil to vinegar |
| Two-stroke fuel | 50 : 1 | Petrol to oil |
Tips
- Ratios are close relatives of fractions — the Fraction Calculator adds, multiplies and simplifies them.
- Want the shares as percentages of something else? Use the Percentage Calculator.
- Sharing a restaurant bill by what each person had? The Split Bill Calculator is made for that.
- Always keep the units the same on both sides of a ratio: compare grams with grams, not grams with kilograms.
Frequently asked questions
Can’t find your answer? Contact us — we reply quickly.
How do I simplify a ratio?
Divide all parts by their greatest common divisor. 24 : 36 has the divisor 12, so it simplifies to 2 : 3.
How do I solve a proportion?
Cross-multiply and divide. In 3 : 4 = 9 : x, multiply 4 × 9 = 36 and divide by 3 to get x = 12.
How do I divide a number in a given ratio?
Add the parts of the ratio, divide the number by that sum and multiply the result by each part. 90 in the ratio 1 : 2 gives 30 and 60.
Can a ratio contain decimals or fractions?
Yes. Multiply all parts by the same number to clear them: 0.5 : 1.25 becomes 2 : 5, and 1/2 : 3/4 becomes 2 : 3.
What is the difference between a ratio and a fraction?
A ratio 2 : 3 compares part to part; the corresponding fractions of the whole are 2/5 and 3/5. A fraction always compares a part with the whole.
Are my numbers stored or sent anywhere?
No. The calculation runs in your browser. Your last inputs are remembered on your own device only, so the form is still filled in when you come back; use Reset to clear them.
More free calculators
Money, dates, maths, health and home projects — quick answers that are worked out in your browser.