Ratio Calculator

It means writing the same relationship with the smallest whole numbers possible. 50:100 and 1:2 describe the identical proportion; 1:2 is just the reduced form, found by dividing both sides by their greatest common divisor.

Multiply both terms by the same power of ten until they are whole numbers, then reduce. 1.5:2 becomes 15:20, which divides down to 3:4. The tool does this scaling for you automatically.

A proportion is a statement that two ratios are equal, written A:B = C:D. If you know any three of the four numbers, the fourth is fixed, which is what the solve mode calculates.

From A:B = C:D, cross-multiplication gives A × D = B × C, so D = B × C ÷ A. Enter A, B and C and the tool applies that formula. This is the classic "rule of three".

Because solving the proportion divides by A. Division by zero is undefined, so a proportion like 0:5 = 3:D has no single answer. The other terms are allowed to be zero.

It rewrites the ratio so the second term is 1, which makes two ratios easy to compare at a glance. 16:9 is about 1.78:1, while 4:3 is 1.33:1 — the larger first number is the wider ratio.

They are closely related. The ratio a:b has the same value as the fraction a/b, and both reduce using the greatest common divisor. A ratio usually compares parts of a whole or two separate quantities, while a fraction names a part of one whole.

Yes. Enter a width and height in simplify mode to get the ratio (1920×1080 → 16:9). If you need to resize while keeping a ratio fixed, the dedicated aspect-ratio calculator adds pixel dimensions on top of this.

Yes. 3:4 and 4:3 are different ratios. Keep the quantities in a consistent order — for a proportion, the first ratio’s order must match the second’s (servings:grams = servings:grams, not servings:grams = grams:servings).

The reduced terms are exact integers. The decimal value and the "n : 1" form are shown to six significant digits, which is enough for everyday scaling; round to whatever your task needs.