Ratio Calculator
Ratio calculator — enter two numbers to simplify the ratio to its lowest terms, with the equivalent decimal and the percentage split between the two parts. Handles whole numbers and decimals. Runs in your browser.
Ratio Calculator
How to Use the Ratio Calculator
Enter the first number
Type the first quantity (a).
Enter the second
Type the second quantity (b).
Read the ratio
See it simplified to lowest terms.
Check the splits
See the decimal and percentage breakdown.
Ratios, Reduced
A ratio is one of the most useful ideas in everyday mathematics: a way of comparing two quantities of the same kind so you can see how much of one there is relative to the other. We meet ratios constantly — the 16:9 of a television, the mix ratio of concrete, the gearing of a bicycle, the scale of a map, the price-to-earnings of a share — yet the single most common task with any ratio is to reduce it to its simplest form. This calculator does exactly that: enter two numbers and it returns the ratio in lowest terms, alongside the decimal equivalent and the percentage split between the two parts.
The method is the same one taught in school: divide both numbers by their greatest common divisor, the largest value that goes into both exactly. Fifty to a hundred both divide by fifty to give one to two; nineteen-twenty to ten-eighty both divide by a hundred and twenty to give sixteen to nine. The calculator computes that greatest common divisor automatically, so you never have to hunt for it by trial and error. It also copes with decimals by scaling them up to whole numbers first, so a measurement like 2.5:5 correctly reduces to 1:2 rather than leaving you with an awkward fractional ratio.
The extra outputs make the result more useful than a bare ratio. The decimal form — the first number divided by the second — turns the comparison into a single value you can compare against another ratio at a glance; a 16:9 ratio reads as roughly 1.78. The percentage split treats the two numbers as parts of a whole, so a 1:3 ratio shows as 25% and 75%, which is exactly what you need when sharing money, a mixture, or a workload in a given proportion. Because equivalent ratios always reduce to the same lowest-terms form, the tool also doubles as a quick check of whether two ratios are equivalent: simplify both and compare. Whether you are resizing an image, splitting a bill, mixing a solution or checking homework, the principle is identical, and as with every RECATOOLS tool, the calculation runs entirely in your browser.
Every ratio, from a TV screen to a concrete mix, reduces the same way — divide both sides by their greatest common divisor.
10 Facts About Ratios
A ratio compares two quantities of the same kind.
Simplify by dividing both by their greatest common divisor.
16:9 is the standard widescreen ratio.
A ratio can be written with a colon or as a fraction.
Equivalent ratios scale by the same factor.
Decimals can be turned into ratios by scaling up.
The golden ratio is approximately 1.618:1.
Aspect, gear and mixing ratios all use the same maths.
A ratio of 1:1 means the parts are equal.
This calculator runs in your browser — nothing is uploaded.
Frequently Asked Questions
- Divide both sides of the ratio by their greatest common divisor — the largest number that divides both evenly. For example, 50:100 both divide by 50 to give 1:2, and 1920:1080 both divide by 120 to give 16:9. This calculator finds the greatest common divisor for you and returns the lowest-terms ratio.
- A ratio compares two quantities of the same kind, showing how much of one there is relative to the other. It can be written with a colon (3:2), as a fraction (3/2), or with the word “to” (3 to 2). Ratios are everywhere — screen dimensions, recipe mixes, gear teeth, map scales and financial figures all use them.
- Yes. If you enter decimal numbers, the calculator scales them up to whole numbers before simplifying, so 2.5:5 correctly becomes 1:2. This is handy when your measurements are not whole numbers but you still want a clean, simplified ratio to work with.
- It is the first number divided by the second, expressing the ratio as a single value. A 16:9 ratio has a decimal of about 1.778, meaning the first quantity is roughly 1.78 times the second. The decimal form makes it easy to compare two ratios at a glance.
- They show what share each part represents of the whole, treating the two numbers as parts of a total. A 1:3 ratio splits as 25% and 75%. This is useful for sharing amounts in a given ratio — dividing a sum of money, a mixture or a workload proportionally.
- Multiply or divide both sides by the same number to get an equivalent ratio. 2:3 scaled by 4 is 8:12, which simplifies back to 2:3. Equivalent ratios always reduce to the same lowest-terms form, which is exactly what this tool computes, so you can check whether two ratios are equivalent.
- They are closely related. A ratio a:b can be written as the fraction a/b, and simplifying a ratio is the same process as simplifying a fraction. The difference is mostly one of interpretation: a fraction usually represents a part of a whole, while a ratio compares two separate quantities.
- Constantly. Screen and image aspect ratios (16:9, 4:3), recipe and concrete mix ratios, gear and pulley ratios, map and model scales, currency and unit conversions, and financial ratios like price-to-earnings all rely on the same simplification maths this calculator performs.
- For whole-number inputs it is exact. For decimal inputs the tool scales to integers first, which is exact for terminating decimals; very long or repeating decimals are handled to a high precision but may round at the extremes. For everyday measurements the result is reliably exact.
- Completely free, with no account or limit. It works offline once the page has loaded and collects no data.
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