Ratio Calculator

This calculator does the three things people need a ratio for. It simplifies a ratio to the smallest whole numbers, so 1920 : 1080 becomes 16 : 9. It finds the missing term of a proportion: if 3 : 4 = 9 : x, then x is 12. And it shares an amount in a ratio, such as ₹1,000 split 2 : 3 : 5, rounding each part so that the parts still add up to the amount exactly.

1. Choose Simplify, Find the missing term, or Share an amount.
2. Type a ratio with colons between the terms, such as 4 : 6 or 1.5 : 2 : 3. Up to ten terms are allowed.
3. To find a missing term, fill in a, b and c in a : b = c : x.
4. To share an amount, type the amount, the ratio, and whether to round to whole units or to two decimal places.

• Terms must be zero or more. A negative ratio has no everyday meaning, so it is refused rather than guessed at.
• Each number can have up to 15 digits. The arithmetic is decimal, not binary, so 0.1 : 0.3 simplifies to 1 : 3 rather than to something slightly off.
• A missing term or a share that does not end is shown to 10 decimal places.
• When a share is rounded, a part can differ from its unrounded value by up to one unit. That is the price of the parts adding up exactly; the unrounded values are listed under the answer.
• All of it is worked out in this page. Nothing you type is sent anywhere or kept, and the calculator works offline once loaded.

Divide every term by the largest number that divides them all, their greatest common divisor. For 12 : 18 that is 6, giving 2 : 3. If a term has decimals, first multiply every term by the same power of ten: 1.5 : 2.25 becomes 150 : 225, then 2 : 3.

Cross-multiply. In a : b = c : x, x is b × c ÷ a. For a 16 : 9 screen 1920 pixels wide, the height is 9 × 1920 ÷ 16 = 1080 pixels.

Because ₹100 split three ways is ₹33.333… each, and you cannot pay a third of a paisa. Rounding each part on its own gives ₹33.33 three times, which loses a paisa. The calculator rounds every part down and gives the leftover units to the parts that lost the most, so here one person gets ₹33.34 and the total is still ₹100.

It is the ratio divided by its first term, sometimes called a unit ratio. 2 : 3 becomes 1 : 1.5, which says there is one and a half times as much of the second thing as of the first.

Yes. Simplify a screen size to find its aspect ratio, use the missing-term mode to resize an image without stretching it, or scale a recipe: if 12 biscuits take 2 cups of flour, then 12 : 2 = 30 : x gives the flour for 30 biscuits, x = 5 cups.