Ratio Calculator (Simplify & Scale)

This ratio calculator simplifies any two-part ratio and shows each side as a percentage. A ratio compares two quantities. This calculator reduces any two-part ratio to its simplest form, shows what each side is worth as a percentage of the total, and lists equivalent ratios so you can scale it to the size you need.

Simplifying

12 : 16 → GCD 4 → 3 : 4

Both parts are divided by their greatest common divisor. When the GCD is 1 the ratio cannot be reduced further.

Parts versus whole

In 3:4 there are 7 parts in total, so A is 3/7 ≈ 42.86% and B is 4/7 ≈ 57.14%. That is different from the fraction 3/4 = 75%, which treats B as the whole — the calculator shows the ratio value A ÷ B and each share of the total so both readings are clear.

Worked example

Reducing a 1920 × 1080 display to its aspect ratio:

GCD(1920, 1080)  = 120
simplified       = 16 : 9
ratio value      = 1920 ÷ 1080 ≈ 1.7778
A share of total = 1920 ÷ 3000 = 64%
B share of total = 1080 ÷ 3000 = 36%

The equivalent-ratios table then scales 16:9 by 2, 3, 5 and 10 to give 32:18, 48:27, 80:45 and 160:90 — the same shape at five different sizes, which is what makes the reduction useful rather than merely tidy. Enter 1366 × 768 and you get 683:384, which is not 16:9 and is one of the reasons laptop screens at that resolution look subtly different.

Parts of a total, not a fraction of one thing

The commonest misreading of a ratio is treating 3:4 as the fraction 3/4. They make different claims. The fraction 3/4 says three parts out of a whole divided into four. The ratio 3:4 says for every 3 of one thing there are 4 of another, and there are 7 in total — so A is 3/7 ≈ 42.86% and B is 4/7 ≈ 57.14%.

Both readings are shown here deliberately. The ratio value A ÷ B = 0.75 is the fraction interpretation, and the two share-of-total percentages are the parts interpretation. When you divide an amount in a given ratio it is the shares you need: to split 250 in the ratio 2:3, add the parts to get 5, divide to get 50 per part, then take 100 and 150. Percentage Calculator handles that last step when the split does not come out round.

Two parts, and whole numbers only

Both inputs are truncated to integers before the GCD is found, so 2.9 becomes 2 rather than 3. That is worth knowing if you are converting a measured ratio: a mixture recorded as 1.5 : 1 should be entered as 3 : 2, which states the same relationship in whole numbers, and the tool will confirm it is already in its lowest terms.

Only two-part ratios are supported. A three-way split such as 2:3:4 has to be handled as two separate comparisons, or worked from the total number of parts directly — 2 + 3 + 4 = 9, so the shares are 2/9, 3/9 and 4/9 of whatever you are dividing. Zero is accepted on either side, because 0:5 meaningfully says one quantity is absent, but 0:0 has no ratio and returns nothing. Fraction Calculator is the better tool once you have turned the ratio into shares, and Average Calculator summarises a list of them.

Private and instant

Everything is computed in your browser with exact integer arithmetic. Nothing is uploaded and no account is needed.