⚖️ Ratio Calculator
Enter a proportion in the form "A:B = C:X" and this tool automatically calculates the value of X. If A and B are whole numbers, it also shows the simplest form of that ratio. Handy for adjusting recipe quantities or calculating map scales.
How to use
- Enter the values for A, B, and C.
- The value of X is calculated automatically.
- If A and B are whole numbers, the simplest form of the ratio is also shown.
How the calculation works
This tool solves the proportion A : B = C : x for x, using the rule that the product of the means equals the product of the extremes: A × x = B × C x = B × C ÷ A It also shows A : B in its simplest whole-number form (divided by the greatest common divisor) when A and B are integers. Use it for anything proportional: scaling recipe quantities, working out real distances from a map scale, or resizing an image while keeping its aspect ratio.
Worked example
4 : 6 = 10 : x x = 6 × 10 ÷ 4 = 15 4 : 6 simplifies to 2 : 3 Recipe example 30 g of sugar for 2 people → how much for 5? 2 : 30 = 5 : x → x = 30 × 5 ÷ 2 = 75 g
Things to be aware of
- A cannot be 0, since that would mean dividing by zero.
- Ratios with decimals are not simplified to whole numbers. Multiply by 10 or 100 first to get the simplified ratio.
- This does not apply to inverse proportions (more people, less time each, for example).
FAQ
How is X calculated?
From the proportion A:B = C:X, X is found using X = (B × C) ÷ A.
Can I enter decimal values?
Yes, A, B, and C can all be decimals. The simplest-ratio display only appears when A and B are whole numbers.
What happens if A is 0?
If A is 0 the calculation can't be performed, so no result is shown.