Decimal to Ratio Calculator
Turn any decimal into a ratio in simplest form, convert a ratio back to a decimal, or change a percent into a ratio. Everything runs in your browser with step-by-step working shown.
Examples to try: 0.5, 0.333, 1.5, 0.125, 2.5
Type it as 3:4, 3/4, or “3 to 4”.
Examples to try: 50%, 150%, 33.3%, 12.5%
Common decimal to ratio conversions
Tap any row to load it into the converter. Rows marked “approx.” are the closest simple ratio, the rest are exact.
| Decimal | Ratio | Fit |
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How to turn a decimal into a ratio
Method 1: exact conversion for terminating decimals
Write the decimal over a power of ten, then divide both parts by their greatest common divisor. For 0.75: write 75/100, divide top and bottom by 25, and you get 3:4. This is how the Exact mode of the calculator works.
Method 2: closest simple ratio for repeating decimals
Decimals like 0.333 never terminate, so the practical answer is the nearest ratio with a small second number. The calculator uses continued fractions to find it: 0.333 becomes 1:3, 0.6667 becomes 2:3, and 0.142857 becomes 1:7. Raise the max denominator setting for tighter fits.
Method 3: ratio back to decimal
Just divide: a ratio of a:b equals the decimal a / b. So 3:4 is 0.75 and 16:9 is about 1.7778. The Ratio to Decimal tab also shows the percent form automatically.
Method 4: percent to ratio
Drop the percent sign and divide by 100, then simplify the decimal as above. 75% is 0.75 which is 3:4, 150% is 1.5 which is 3:2, and 12.5% is 0.125 which is 1:8.
Ratios in real life
Betting odds
Decimal odds and fractional odds are the same idea written two ways.
Aspect ratios
Screens, photos, and video frames all use width:height ratios.
Recipes
Ratios let you scale any recipe up or down without redoing the math.
Methodology
This decimal to ratio converter finds the best whole-number ratio with a denominator up to a chosen limit (100 by default) using continued fractions, the classic number-theory technique for best rational approximation. Terminating decimals can also be converted exactly from their typed digits. The greatest common divisor step guarantees every answer is in simplest form, so 75:100 is always reported as 3:4. All math runs locally in your browser; no input ever leaves your device.
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Frequently asked questions
How do I convert 0.75 to a ratio?
Type 0.75 into the converter and you get 3:4. Behind the scenes, 0.75 equals 75/100, and dividing both parts by their greatest common divisor (25) gives 3:4, which is the simplest whole-number ratio.
What is 0.5 as a ratio?
0.5 as a ratio is 1:2. It equals 5/10, and dividing both numbers by their greatest common divisor (5) leaves 1:2. Anything that is half of something, like a 50% mix, is a 1:2 ratio.
What is 0.333 as a ratio?
0.333 converts to approximately 1:3. Because 0.333 does not match a small whole-number ratio exactly, the tool finds the closest simple ratio, and 1:3 equals 0.3333..., which is off by only about 0.000333. If you need the exact fraction of the typed digits instead, switch to Exact mode to get 333:1000.
What is 1.5 as a ratio?
1.5 as a ratio is 3:2. It equals 15/10, and dividing both parts by 5 gives 3:2. Decimals larger than 1 simply produce ratios where the first number is bigger than the second, such as 2.5 converting to 5:2.
How do I convert a ratio like 3:4 back to a decimal?
Divide the first number by the second: 3 / 4 = 0.75. Use the Ratio to Decimal tab and type 3:4 (or 3/4, or "3 to 4") to get 0.75 instantly. Another example: 16:9 converts to about 1.7778.
How do I convert a percentage to a ratio?
Drop the percent sign and divide by 100, then simplify. For example, 75% becomes 0.75, which simplifies to 3:4. Other conversions: 150% is 3:2, 33.3% is about 1:3, and 12.5% is 1:8.
Why does 0.333 give 1:3 instead of 333:1000?
That is the difference between the two modes. Simplest-ratio mode looks for the closest ratio with a small denominator (up to 100 by default), so 0.333 becomes the easy-to-use approximation 1:3. Exact mode skips the approximation and converts the typed digits literally, giving 333:1000. Use Simplest for everyday use and Exact when every digit matters.
What does "simplest form" of a ratio mean?
A ratio is in simplest form when its two numbers share no common divisor other than 1. For example, 75:100 simplifies to 3:4 because both divide by 25. This tool always reduces results, so you never get 75:100 when 3:4 says the same thing.
Can I convert decimals greater than 1 or negative decimals?
Yes. Decimals greater than 1 give ratios like 2.5 to 5:2 and 1.5 to 3:2. Negative decimals keep the minus sign on the first number, so -0.75 becomes -3:4. Zero converts to 0:1.
How accurate is the approximation for repeating decimals?
The tool finds the closest ratio whose second number is at most 100 by default, which is plenty for practical use: 0.6667 becomes 2:3, 0.1667 becomes 1:6, and 0.142857 becomes 1:7. Even 3.14159 lands on the classic 311:99. You can raise the denominator limit to 1000 for tighter fits.
How are decimals and ratios used in betting odds?
Odds are just ratios in disguise. Fractional odds of 3:1 mean you profit 3 units for every 1 unit staked, which implies a 1 in 4 (25%) chance since 1/(3+1) = 0.25. Convert between formats with the Ratio to Decimal tab: 3:1 becomes 3.0 as a decimal-style multiplier base.
How do ratios work in cooking and recipes?
Recipes scale cleanly with ratios. A rice-to-water ratio of 2:3 means 2 cups of rice need 3 cups of water, and 4 cups of rice need 6 cups. If a recipe gives a decimal like 0.75 cups of sugar per 1 cup of flour, that is a 3:4 ratio, so doubling means 1.5 cups of sugar per 2 cups of flour.
What is an aspect ratio like 16:9 as a decimal?
Divide 16 by 9 to get about 1.7778. The Ratio to Decimal tab does this for any aspect ratio: 4:3 becomes 1.3333, and 1:1 stays 1. Going the other way, a decimal width factor of 1.5 is the ratio 3:2.
Is this decimal to ratio calculator free and private?
Yes. It is free, runs entirely in your browser with no account and no data sent to any server, and works offline once the page loads. Everything on this page, including all 20 rows of the common conversion table, is computed on your device.
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