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Ratio Calculator - Simplify, Scale, Divide an Amount and Convert to Percentages

Type a ratio with two or three parts and choose what you need: its simplest form, the same ratio scaled to a new value, an amount shared out in that ratio, or each part as a percentage.

Maintained by Hirantha Sandaruwan Lakshan. Updated 13 October 2026.

About this tool

Decimals are scaled to whole numbers before the greatest common divisor is found, so there is no rounding error, and shares of money add up to the amount exactly. Nothing you type leaves your browser.

How it works

To simplify a ratio, divide every part by their greatest common divisor (GCD), the largest whole number that divides all of them. 40 : 60 has a GCD of 20, so it simplifies to 2 : 3. The GCD is found with Euclid's algorithm: replace the larger number by its remainder when divided by the smaller, and repeat until the remainder is 0. For 1071 and 462 that gives 21, so 1071 : 462 is 51 : 22.

Decimals are removed first by multiplying every part by the same number. 1.5 : 2.5 is 3/2 : 5/2, so multiplying by 2 gives 3 : 5. The tool reads each decimal exactly as a fraction, so 0.1 : 0.3 is 1 : 3 and not the 0.33333333333333337 that floating-point division gives. A part may be 0 (4 : 0 : 6 simplifies to 2 : 0 : 3), but at least one part must be above 0, and parts cannot be negative.

To scale a ratio, say which part you know the new value of. The scale factor is the new value divided by the old part, and every part is multiplied by it. For 3 : 2 with the first part becoming 12, the factor is 12 / 3 = 4, so the ratio becomes 12 : 8. In the form A : B = C : ?, the missing value is B x C / A. You cannot scale from a part that is 0, because 0 times any factor is still 0.

To divide an amount in a ratio, add the parts, divide the amount by that total, and multiply by each part. Rs. 10,000 in 3 : 2 has 5 parts, each worth Rs. 2,000, so the shares are Rs. 6,000 and Rs. 4,000. When the shares are not whole cents, each is rounded down and the leftover cents go to the shares with the largest fractions (the largest remainder method). When two fractions are equal, this tool gives the extra cent to the earlier share first. So Rs. 1,000 in 1 : 1 : 1 gives Rs. 333.34, Rs. 333.33 and Rs. 333.33, and the shares always add up to the amount.

To turn a ratio into percentages, divide each part by the total and multiply by 100. 2 : 3 means 2/5 and 3/5 of the whole, which is 40% and 60%. To go the other way, type the percentages as the parts: 60 : 40 simplifies to 3 : 2.

Worked examples

Simplify 40 : 60 and 8 : 12 : 20

40 : 60 divided by 20 is 2 : 3. For 8 : 12 : 20 the GCD is 4, so it simplifies to 2 : 3 : 5.

Scaling a mix

Flour and sugar in the ratio 2 : 3, and you have 500 g of flour. The factor is 500 / 2 = 250, so you need 3 x 250 = 750 g of sugar: 2 : 3 = 500 : 750.

Sharing Rs. 10,000 in the ratio 3 : 2

3 + 2 = 5 parts, each worth Rs. 2,000. The shares are Rs. 6,000 and Rs. 4,000.

Sharing Rs. 1,000 in three equal parts

1 : 1 : 1 is exactly 333.333... each, which cannot be paid to the cent. The shares are Rs. 333.34, Rs. 333.33 and Rs. 333.33, which add up to exactly Rs. 1,000.00.

Two apples and three oranges

The ratio 2 : 3 means apples are 2/5 of the fruit (40%) and oranges are 3/5 (60%).

Common ratios as fractions and percentages

RatioFraction of the wholePercentages
1 : 11/2 and 1/250% and 50%
1 : 21/3 and 2/333.333333% and 66.666667%
1 : 31/4 and 3/425% and 75%
2 : 32/5 and 3/540% and 60%
3 : 23/5 and 2/560% and 40%
3 : 73/10 and 7/1030% and 70%
4 : 14/5 and 1/580% and 20%
1 : 1 : 11/3, 1/3 and 1/333.333333% each
1 : 2 : 31/6, 1/3 and 1/216.666667%, 33.333333% and 50%

Frequently asked questions

How do I simplify a ratio?

Divide every part by their greatest common divisor. For 40 : 60 the GCD is 20, so the ratio is 2 : 3. If the only common divisor is 1, the ratio is already in its simplest form, like 3 : 2.

How do I simplify a ratio with decimals?

Multiply every part by the same number to make them whole, then simplify. 1.5 : 2.5 multiplied by 2 is 3 : 5. Multiplying by 10 first (15 : 25) and then dividing by 5 gives the same answer. The calculator does this exactly, with no floating-point error.

How do I find a missing value in a ratio?

Work out the scale factor from the part you know, then multiply the others. If 3 : 2 = 12 : ?, the factor is 12 / 3 = 4, so the missing value is 2 x 4 = 8. In general, for A : B = C : ?, the missing value is B x C / A.

How do I divide an amount in a ratio?

Add the parts, divide the amount by the total to get the value of one part, and multiply by each part. Rs. 10,000 in the ratio 3 : 2 has 5 parts of Rs. 2,000, so the shares are Rs. 6,000 and Rs. 4,000. The calculator also handles three parts and decimals.

How do I convert a ratio to a percentage?

Divide each part by the sum of the parts and multiply by 100. For 3 : 2 the total is 5, so the parts are 3/5 = 60% and 2/5 = 40%.

Can a ratio have a zero part?

Yes, as long as at least one part is above 0. 4 : 0 : 6 simplifies to 2 : 0 : 3, and in a division the zero part gets nothing. You cannot scale a ratio from a part that is 0, and 0 : 0 has no meaning.

What is the difference between a ratio and a fraction?

A ratio compares parts with each other (3 : 2). A fraction compares a part with the whole (3/5). A ratio of 3 : 2 means the whole is 5 parts, so the parts are 3/5 and 2/5 of it.

Can I use more than three parts?

Not in this tool: it handles two or three parts. For a longer ratio, simplify it by dividing every part by their greatest common divisor, which works the same way for any number of parts.

Is anything I type sent to a server?

No. The sums run in your browser and nothing is stored or sent anywhere.

Updated Oct 13, 2026