What is a ratio calculator?
A ratio calculator helps you work with ratios in three common ways: simplify a ratio to its lowest terms, solve a proportion such as A : B = C : x, and divide an amount in a given ratio. This online ratio calculator finds the ratio between two numbers or three numbers (decimals included) and shows the answer with the working, the equivalent percentages and a chart of the shares. Use it for screen resolutions and aspect ratios, recipes, cement and paint mixes, profit sharing and maths homework.
What is ratio?
A ratio compares two or more quantities of the same kind by division. It is written with a colon – 3 : 2, read "3 to 2" – and tells you how many times one amount contains another. If a class has 18 girls and 12 boys, the ratio of girls to boys is 18 : 12, which simplifies to 3 : 2. The order matters: boys to girls is 2 : 3. A proportion is a statement that two ratios are equal, such as 3 : 2 = 18 : 12.
How to use the ratio calculator
- Simplify a ratio: enter A and B (and C for a three-part ratio). The calculator gives the simplest form, the 1 : n form and each part as a percentage.
- Solve a proportion: enter A, B and C of A : B = C : x to find x.
- Divide an amount: enter the ratio and the amount to see each person's or ingredient's share.
How to calculate ratio of 2 numbers (simplify)
To simplify a ratio, divide every part by their greatest common divisor (GCD). The default example is a Full HD screen of 1920 × 1080 pixels:
- GCD of 1920 and 1080 = 120 (the GCD calculator shows the prime factor steps).
- 1920 ÷ 120 = 16 and 1080 ÷ 120 = 9.
- So the ratio in simplest form is 16 : 9.
If the ratio has decimals, multiply all parts by the same power of 10 first: 1.5 : 2.25 becomes 150 : 225, which simplifies to 2 : 3. With fractions, multiply by the common denominator: 1/2 : 1/3 becomes 3 : 2.
How to calculate ratio of 3 numbers
For a ratio of three numbers, find the GCD of all three and divide. 24 : 36 : 60 has a GCD of 12, so it simplifies to 2 : 3 : 5. Enter the third value in the "C" box to use the ratio calculator for 3 numbers.
Ratio and proportion: solve for x
When two ratios are equal, cross-multiplication gives the missing value:
A : B = C : x → x = (B × C) ÷ A
- A, B = the known ratio
- C = the known value in the second ratio
- x = the unknown value
Example – resize an image: an image is 1920 × 1080 and you want it 1280 px wide. 1920 : 1080 = 1280 : x, so x = 1080 × 1280 ÷ 1920 = 720 px. That is how every aspect ratio calculator works for width and height, pixels and screen resolutions.
Example – recipe: 250 g flour needs 150 ml milk. For 400 g flour: 250 : 150 = 400 : x, x = 150 × 400 ÷ 250 = 240 ml.
Dividing an amount in a ratio
To split a total in a ratio, add the parts, find the value of one part, then multiply.
Share = Total × (part ÷ sum of parts)
Example – profit sharing: three partners share a profit of ₹90,000 in the ratio 2 : 3 : 4. Total parts = 9, one part = ₹10,000, so the shares are ₹20,000, ₹30,000 and ₹40,000. Partnership firms in India often write the profit-sharing ratio into the partnership deed; for the profit itself, see the profit margin calculator.
Example – concrete mix: M20 concrete is often mixed at 1 : 1.5 : 3 (cement : sand : aggregate). For 5.5 parts in total, a batch of 1,100 kg of dry material needs 200 kg cement, 300 kg sand and 600 kg aggregate.
Ratio to percentage
To convert a ratio to percentages, divide each part by the total and multiply by 100. In 3 : 2 the total is 5, so the first part is 60% and the second 40%. For 2 : 3 : 5 the shares are 20%, 30% and 50%. The calculator lists these under every simplified ratio. To go the other way, write the percentages as a ratio and simplify: 75% : 25% = 3 : 1. For more percentage problems use the percentage calculator.
Ratios and fractions
A two-part ratio A : B can be written as the fraction A/B, comparing part to part. The fraction of the whole is different: in 3 : 2, the first part is 3/5 of the total, not 3/2. Keep this in mind for questions like "the ratio of boys to girls is 2 : 3; what fraction are boys?" – the answer is 2/5. The fraction calculator can simplify and convert these.
Common ratios in daily life
| Use | Typical ratio | Meaning |
|---|---|---|
| TV, laptop, YouTube video | 16 : 9 | 1920 × 1080, 1280 × 720, 3840 × 2160 |
| Instagram portrait post | 4 : 5 | 1080 × 1350 px |
| Reels, Shorts, stories | 9 : 16 | 1080 × 1920 px |
| Pour-over coffee | 1 : 15 to 1 : 17 | 1 g coffee to 15–17 ml water |
| Rice to water (open pot) | 1 : 2 | 1 cup rice to 2 cups water |
| Plastering mortar | 1 : 4 or 1 : 6 | cement : sand |
| Dilution, 1 : 10 | 1 : 9 by volume | 1 part concentrate in 10 parts total |
Note the dilution convention: "1 : 10" in labs often means 1 part in 10 total (1 part concentrate + 9 parts water), while mixing instructions on paint or cleaning products usually mean 1 part to 10 parts. Check which one is intended before mixing liquids in ml.
Ratio analysis in accounting
Businesses use financial ratios to judge health: current ratio = current assets ÷ current liabilities (above 1.5 is usually comfortable), debt-to-equity = total debt ÷ shareholders' equity, and net profit ratio = net profit ÷ revenue × 100. These are ratios in the "n : 1" form, so use the simplify mode and read the "n : 1" line.
How to compute a ratio on a calculator
On an ordinary calculator, divide the first number by the second: 1920 ÷ 1080 = 1.7778, which means 1.78 : 1. To get whole numbers, divide both by the smaller one or by their GCD. In Excel, use =A1/GCD(A1,B1)&":"&B1/GCD(A1,B1) to show a simplified ratio.
Ratio calculator formula
The ratio calculator formula for simplifying is A : B = (A ÷ GCD) : (B ÷ GCD), where GCD is the greatest common divisor. For a proportion A : B = C : x, the formula is x = B × C ÷ A. To split a total T in the ratio A : B, each share is T × A ÷ (A + B) and T × B ÷ (A + B).
Ratio calculator: ml, oz and cups for mixing liquids
A ratio calculator for mixing tells you how much of each liquid to use. For a 1 : 4 concentrate-to-water mix in a 500 ml bottle, choose "Divide an amount", enter 1 and 4, and a total of 500: the result in ml is 100 ml of concentrate and 400 ml of water. The same method for liquid works in oz: a 1 : 3 mix in 32 oz is 8 oz and 24 oz. The units do not matter as long as you use the same unit for every part, and a liquid answer in cups works the same way (2 cups in a 1 : 1 mix is 1 cup each).
Ratio calculator: volume, grams and kg
Ratios by volume and ratios by weight are different. A 1 : 2 : 3 cement, sand and aggregate mix by volume in 0.6 m³ gives 0.1, 0.2 and 0.3 m³. For a ratio calculator in grams or kg, split the weight instead: 1 kg in a 3 : 2 ratio is 600 g and 400 g.
Ratio calculator for recipes and baking
Bakers use ratios so recipes scale. Bread is often around 5 parts flour to 3 parts water by weight. A ratio calculator for recipes solves the proportion: if 500 g flour needs 300 g water, then 800 g flour needs 300 × 800 ÷ 500 = 480 g. A ratio calculator for baking also handles cups: 3 cups flour to 1 cup sugar, scaled to 2 cups of flour, needs 2/3 cup sugar.
Ratio calculator image guide: aspect ratio in pixels and inches
The default example, 1920 : 1080, simplifies to 16 : 9. To resize an image and keep its ratio, solve 1920 : 1080 = 1280 : x, giving x = 720. For a print in inches, a 4 : 3 ratio at 12 inches wide is 9 inches tall.
Ratio calculator: bike gear ratio
A bike gear ratio is chainring teeth ÷ rear sprocket teeth. 48 teeth at the front and 16 at the back is 48 : 16 = 3 : 1, so the rear wheel turns 3 times per pedal turn.
Ratio calculator childcare guide: nursery and early years staffing
Early years settings must keep a minimum number of adults for the number of children, and the required ratio depends on the children's ages and the country's rules. To check a room, divide the number of children by the number of staff: 18 children with 3 staff is 6 : 1. Use the ratio calculator's proportion mode to find how many staff you need: at 1 : 8, 30 children need 30 ÷ 8 = 3.75, so 4 adults. Always check the current rules from your regulator.
Debt to income ratio calculator: yearly or monthly
A debt-to-income ratio divides debt payments by gross income. Monthly: ₹18,000 of EMIs on ₹60,000 income is 30%. Yearly gives the same answer if you use yearly figures for both: ₹2,16,000 ÷ ₹7,20,000 = 30%. Lenders in India often prefer total EMIs below about 40–50% of income.
Ratio calculator questions with answers
- Simplify 45 : 60. GCD is 15, so 3 : 4.
- Share ₹1,200 in the ratio 2 : 3 : 5. Parts total 10, so ₹240, ₹360 and ₹600.
- If 3 : 5 = 12 : x, find x. x = 5 × 12 ÷ 3 = 20.
- A map scale is 1 : 50,000. How far is 4 cm on the map? 4 × 50,000 = 200,000 cm = 2 km.
Best ratio for an Instagram post
Instagram feed posts are commonly 4 : 5 portrait (1080 × 1350 pixels) or 1 : 1 square (1080 × 1080). Portrait 4 : 5 takes up the most screen space in the feed. Use the proportion mode to scale: 4 : 5 = 1440 : x gives x = 1800.
Ratios and rational numbers
What is a rational number? It is any number you can write as a ratio of two integers, p : q or p/q, with q not zero. So 0.75 is rational because it equals 3 : 4, while √2 and π are not.
Sharpe ratio calculation from monthly returns
For a Sharpe ratio calculation with monthly returns, subtract the monthly risk-free rate from the average monthly return, divide by the standard deviation of monthly returns, and multiply by √12 to annualise. An average excess return of 0.8% with an SD of 3% gives 0.8 ÷ 3 × 3.46 ≈ 0.92.
Related tools and next steps
These free calculators help with the questions people usually have next:
Frequently asked questions
How do you calculate a ratio between two numbers?
Write the numbers as A : B and divide both by their greatest common divisor. 1920 : 1080 divided by 120 gives 16 : 9.
How do I solve a proportion for x?
For A : B = C : x, cross-multiply: x = B × C ÷ A. For 4 : 5 = 12 : x, x = 5 × 12 ÷ 4 = 15.
How do I divide an amount in a ratio?
Add the ratio parts, divide the amount by that total to get one part, then multiply by each part. ₹90,000 in 2 : 3 : 4 gives ₹20,000, ₹30,000 and ₹40,000.
How do I convert a ratio to a percentage?
Divide each part by the sum of all parts and multiply by 100. In 3 : 2, the parts are 60% and 40%.
Can the ratio calculator handle 3 numbers and decimals?
Yes. Enter a third value in C for ratios like 2 : 3 : 5, and use decimals freely; the calculator scales them to whole numbers before simplifying.
What is the difference between a ratio and a proportion?
A ratio compares quantities, such as 3 : 2. A proportion says two ratios are equal, such as 3 : 2 = 12 : 8, and is used to find a missing value.
Is this ratio calculator free?
Yes, the ratio calculator is free, needs no sign-up and works on phones and computers.
How do I mix a 1:4 ratio in ml?
Add the parts (1 + 4 = 5), divide the total volume by 5 and multiply. For 1 litre, use 200 ml of the first liquid and 800 ml of the second.
What is the formula to solve a ratio for x?
For A : B = C : x, x = B × C ÷ A.
Can I use this ratio calculator for pixels and resolution?
Yes. Enter width and height, such as 2560 and 1440, to get 16 : 9. As a ratio calculator for pixels it also finds the missing height or width for any resolution.
Is this a ratio calculator with 3 numbers?
Yes. Fill in the optional C box. The ratio calculator 3 numbers mode simplifies 12 : 18 : 24 to 2 : 3 : 4.
Does it work as a ratio calculator for 2 numbers in ml or kg?
Yes. Use any unit; the ratio calculator in ml, grams or kg gives the same split as long as all parts share one unit.
How do I turn a ratio into a percentage?
Divide each part by the total and multiply by 100. As a ratio calculator in percentage terms, 3 : 1 is 75% and 25%.
How do I use a ratio calculator for early years staffing?
Divide children by adults to get the current ratio, then compare with your regulator's required ratio for that age group.
Last updated 2026-10-14 · Formula and worked examples checked by the CodingMarble team · How we check every calculator