How do I simplify a ratio?

Divide both sides by their greatest common divisor. 18:24 both divide by 6, giving 3:4.

How do I solve a ratio with a missing number?

Cross-multiply. For 3:4 = 9:x, multiply 4 × 9 = 36 and divide by 3, so x = 12.

How do I convert a ratio to a percentage?

Divide the first number by the total of both parts and multiply by 100. In 3:4 the first part is 3 ÷ 7 × 100 = 42.86%, and the second is 57.14%.

How do I turn a ratio into a fraction?

A ratio of A:B becomes the fraction A/B when you compare the two parts, or A/(A+B) when you compare the first part to the whole. 3:4 is 3/4 as a comparison and 3/7 of the total.

How do I convert a ratio to a decimal?

Divide the first number by the second. 3:4 becomes 3 ÷ 4 = 0.75, and 16:9 becomes 1.7778.

How do I scale a ratio up or down?

Multiply both sides by the same number. 3:4 doubled is 6:8; halved it is 1.5:2. The relationship stays identical.

How do I simplify a three-part ratio?

Find the greatest common divisor of all three numbers and divide each part by it. 10:20:30 all divide by 10, giving 1:2:3.

What is the difference between a ratio and a fraction?

A ratio compares two parts to each other (3:4 means 3 for every 4). A fraction compares a part to the whole (3/7 of the total). Same numbers, different bases.

How do I split an amount in a given ratio?

Add the parts to get the total number of shares, divide the amount by that, then multiply by each part. Splitting $700 in 3:4 gives 7 shares of $100, so $300 and $400.

How do I resize an image and keep the same aspect ratio?

Divide the new width by the old width to get a scale factor, then multiply the old height by it. A 1920×1080 image at 1280 wide becomes 1280 × 1080 ÷ 1920 = 720 tall.

Percentage Calculator / Ratio calculator

Ratio Calculator

Simplify a ratio to its lowest terms, solve for a missing value, scale a ratio up or down, work with three-part ratios, turn a ratio into a fraction, decimal or percentage, or resize by aspect ratio. Free, ad-free, and every answer updates as you type.

Simplify and solve

Simplify a ratio

Reduce:

3:4

Solve A : B = C : ?

:=: ?

Ratios as percentages, fractions and shares

Ratio to percentage

The ratio:as percentages

42.86% and 57.14%

Ratio to fraction and decimal

Convert:

3/4 · 0.75 · 42.86% of the total

Split an amount by a ratio

Splitin the ratio:

300 and 400

Three-part ratios, scaling and aspect ratio

Simplify a three-part ratio

Reduce::

1:2:3

Equivalent ratio (scale up or down)

Scale:by×

15:20

Resize by aspect ratio

Original×, new width

1,280 × 720

How to work with ratios step by step

A worked example using 18:24.

1. Find what divides both sides
6 divides 18 and 24
2. Divide both sides by it
18 ÷ 6 = 3, 24 ÷ 6 = 4 → 3:4
3. Add the parts for the total
3 + 4 = 7 shares
4. Convert to percentages
3 ÷ 7 = 42.86%, 4 ÷ 7 = 57.14%

To solve a proportion, cross-multiply: for 3:4 = 9:x, x = 4 × 9 ÷ 3 = 12. Scaling works the same way — multiply both sides by the same number and the ratio is unchanged.

Ratio, fraction, percentage — same numbers, different bases

A ratio of 3:4 compares two parts to each other. As a fraction of the whole it is 3/7, and as a percentage 42.86%. Mixing the bases is the usual mistake: 3:4 is not 3/4 or 75% of the total.

Ratios show up everywhere numbers get shared or scaled — splitting a bill unevenly, mixing paint or concrete, scaling a recipe, screen aspect ratios, or dividing profit between partners. In every case the method is the same: add the parts, find one share, then multiply back out.

Three-part ratios and equivalent ratios

A three-part ratio like 2:3:5 works exactly the same way — add the parts for the total number of shares (10 here), divide the amount by that, then multiply by each part. To simplify, divide all three parts by the largest number that goes into every one of them: 10:20:30 becomes 1:2:3.

Two ratios are equivalent when one is a multiple of the other. 3:4, 6:8, 9:12 and 30:40 are all the same relationship, so they all reduce to 3:4. That is the quickest way to check whether two ratios match: simplify both and compare.

Common ratio answers

Simplified ratios, their decimals and their percentage equivalents.

Simplify 18:243:4

Simplify 20:502:5

Simplify 45:603:4

Simplify 100:2502:5

Simplify 16:916:9

Simplify 12:361:3

Simplify 10:20:301:2:3

Simplify 4:6:82:3:4

1:1 as percentages50% / 50%

1:2 as percentages33.33% / 66.67%

1:3 as percentages25% / 75%

2:3 as percentages40% / 60%

3:4 as percentages42.86% / 57.14%

3:4 as a decimal0.75

16:9 as a decimal1.7778

4:3 as a decimal1.3333

$700 split 3:4$300 and $400

$1,000 split 2:3:5$200, $300, $500

Common aspect ratios

Standard screen and image ratios, and the sizes they match.

1920 × 108016:9

1280 × 72016:9

3840 × 216016:9

1080 × 10801:1

1080 × 13504:5

1080 × 19209:16

1024 × 7684:3

2560 × 108021:9

1200 × 63040:21

Ratio questions people ask

How do I simplify a ratio?: Divide both sides by their greatest common divisor. 18:24 both divide by 6, giving 3:4.
How do I solve a ratio with a missing number?: Cross-multiply. For 3:4 = 9:x, multiply 4 × 9 = 36 and divide by 3, so x = 12.
How do I convert a ratio to a percentage?: Divide the first number by the total of both parts and multiply by 100. In 3:4 the first part is 3 ÷ 7 × 100 = 42.86%, and the second is 57.14%.
How do I turn a ratio into a fraction?: A ratio of A:B becomes the fraction A/B when you compare the two parts, or A/(A+B) when you compare the first part to the whole. 3:4 is 3/4 as a comparison and 3/7 of the total.
How do I convert a ratio to a decimal?: Divide the first number by the second. 3:4 becomes 3 ÷ 4 = 0.75, and 16:9 becomes 1.7778.
How do I scale a ratio up or down?: Multiply both sides by the same number. 3:4 doubled is 6:8; halved it is 1.5:2. The relationship stays identical.
How do I simplify a three-part ratio?: Find the greatest common divisor of all three numbers and divide each part by it. 10:20:30 all divide by 10, giving 1:2:3.
What is the difference between a ratio and a fraction?: A ratio compares two parts to each other (3:4 means 3 for every 4). A fraction compares a part to the whole (3/7 of the total). Same numbers, different bases.
How do I split an amount in a given ratio?: Add the parts to get the total number of shares, divide the amount by that, then multiply by each part. Splitting $700 in 3:4 gives 7 shares of $100, so $300 and $400.
How do I resize an image and keep the same aspect ratio?: Divide the new width by the old width to get a scale factor, then multiply the old height by it. A 1920×1080 image at 1280 wide becomes 1280 × 1080 ÷ 1920 = 720 tall.

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