To simplify a ratio, enter its two parts into the Ratio Calculator and it reduces them to lowest terms. To solve a proportion A:B = C:?, enter the three known values and it finds the missing one.
Follow along with the free Ratio Calculator, which runs in your browser, or browse more tools in this category.
How to use the Ratio Calculator
- Choose simplify or solve for the missing value.
- Enter the numbers.
- Read the simplified ratio or the missing term.
- Check the result by cross-multiplying.
Worked example
The ratio 8:12 simplifies to 2:3. For 2:3 = 10:?, the missing value is 15, because 10 divided by 2 is 5 and 3 times 5 is 15.
Tips and common mistakes
- A ratio is simplified by dividing both parts by their greatest common factor.
- Keep units consistent on both sides of a proportion.
- Cross-multiplication is a quick check: A x ? should equal B x C.
Frequently asked questions
What is a proportion?
An equation stating that two ratios are equal.
Can I use decimals?
Yes, but whole numbers give the cleanest simplified ratios.
Is it private?
Yes. It runs in your browser.