How to simplify a ratio
To simplify a ratio, divide both numbers by their greatest common divisor (GCD). For 16:9 the GCD is 1, so it's already in lowest terms; as a decimal it's about 1.78 to 1. A ratio like 50:100 reduces to 1:2.
Simplifying does not change what a ratio means — 50:100 and 1:2 describe exactly the same proportion, just with smaller numbers. If the two sides share no common factor above 1, as with 16 and 9, the ratio is already as simple as it gets. Setting two ratios equal to each other gives a proportion, solved by the proportion calculator.
How to use this calculator
Enter the two numbers (whole numbers work best). The result shows the ratio in its simplest form and as a decimal. Ratios describe aspect ratios, mixing proportions, odds and scale.
Both entries must be in the same unit before you start. Comparing 30 minutes with 2 hours is not 30:2 but 30:120, which reduces to 1:4. If your figures contain decimals, multiply both by the same power of ten first to clear them, then simplify the whole numbers that remain. A ratio of a part to the whole becomes a percentage through the percentage calculator.
Where ratios are used
The decimal form is often the more practical one. A 16:9 screen is about 1.78 times as wide as it is tall, which is what makes different aspect ratios directly comparable at a glance.
- Screens and images: 16:9 and 4:3 aspect ratios.
- Mixing: concrete, fuel and paint recipes given as part-to-part.
- Scale models and maps: 1:100 means one unit stands for a hundred.
- Finance: debt-to-equity and other comparison figures.
To scale a recipe or a drawing, multiply both sides by the same factor — the proportion stays intact however large the numbers become. Reducing a ratio to its simplest form means dividing both terms by their greatest common factor.
Frequently asked questions
- How do I simplify a ratio?
- Divide both numbers by their greatest common divisor. 50:100 divided by 50 is 1:2.
- What is 16:9 as a decimal?
- About 1.78 to 1 (16 ÷ 9).
- What is a ratio?
- A comparison of two quantities showing how many times one contains the other, written a:b.
- How do I scale a ratio?
- Multiply both sides by the same number. 1:2 scaled by 3 is 3:6.
- What is the difference between a ratio and a fraction?
- A ratio compares two parts to each other, while a fraction compares a part to the whole. In a 1:2 mix there are three shares in total, so the first ingredient is 1/3 of the mixture — not 1/2, which is the usual mistake.