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Ratio calculator

Simplify a ratio to its lowest terms and see it as a decimal.

Related tools

All Percentages & ratios tools →
Golden Ratio CalculatorSplit a length in the golden ratio φ = (1+√5)/2: give the total, the larger or the smaller segment and get the other two, drawn to scale.Odds Ratio CalculatorCompute the odds ratio from a 2×2 table with its log-odds standard error, the Wald interval at 90/95/99 %, relative risk, risk difference — and the Haldane–Anscombe correction when a cell is zero.Percentage calculatorFour percentage calculations in one: X% of Y, what percent X is of Y, and increasing or decreasing a value by a percentage.Percent to Fraction CalculatorConvert a percentage into its reduced fraction and equivalent decimal (e.g. 12.5% → 1/8).Percentage change calculatorFind the percentage increase or decrease between two numbers.Percentage decrease calculatorHow far a value fell from an old figure to a new one, as a percentage — and the absolute drop. A negative result means it actually rose.Percentage difference calculatorCompute the percentage difference between two values (relative to their average).Percentage error calculatorCompute the percentage error between a measured and a true value.

Enter First value, Second value and the Ratio calculator works out Simplified ratio, As decimal straight away. For instance, with First value = 16 and Second value = 9 it returns Simplified ratio = 16:9 and As decimal = 1.778.

How to use it

  1. Enter your values: First value, Second value.
  2. Read the result instantly: Simplified ratio, As decimal.

Frequently asked questions

How does the Ratio calculator work?

It takes First value and Second value and derives Simplified ratio and As decimal from them. The calculation is live as you type, so the result updates on every change.

Which values does the calculator ask for?

2 values: First value and Second value. Nothing else is required — no account, no file upload.

What does a typical calculation look like?

With First value = 16 and Second value = 9, the calculator returns Simplified ratio = 16:9 and As decimal = 1.778. Those figures come from running this exact tool, so you can reproduce them by entering the same values.

What does it give for smaller values?

Scaled down to First value = 8 and Second value = 5, As decimal comes out at 1.6. The relationship is worth checking at both ends before you rely on a single result.

When would I actually use this?

The everyday cases: a discount at the till, a rise or fall between two figures, the price before tax, and working backwards from a total.

What is the most common mistake?

Undoing a percentage by applying it again. Take 20% off 100 and you get 80; add 20% to 80 and you get 96, not 100 — the two operations use different bases.

What is the difference between the Ratio calculator and the Golden Ratio Calculator?

This one returns Simplified ratio and As decimal; the Golden Ratio Calculator returns Result. That is the whole difference — open the one whose figure you need.

Is there a tool for the next step?

Odds Ratio Calculator is the closest one after this: Compute the odds ratio from a 2×2 table with its log-odds standard error, the Wald interval at 90/95/99 %, relative risk, risk difference — and the Haldane–Anscombe correction when a cell is zero.

What else is worth having open alongside it?

Percentage calculator and Percent to Fraction Calculator — they come up in the same task often enough to be worth a second tab.

Where do the figures come from, and how current are they?

Percentage arithmetic is exact and universal. Where a result is a rate rather than an amount, the tool states the base it was taken on, because that is where the ambiguity lives.

Further reading

All guides →
How-toHow to Simplify a RatioDivide both sides by their greatest common divisor. Here's what a ratio is, how to reduce it, why units must match first, and how to compare ratios.How-toLCM and GCD ExplainedThe GCD is the biggest shared divisor; the LCM is the smallest shared multiple. Here's what each means, how to find them with prime factors, and the shortcut linking them.ExplainerRoman Numerals ExplainedSeven letters, added or subtracted. Here's what each stands for, how the subtractive pairs work, how to write any number, and where they still appear.How-toHow to Convert a Percentage to a Fraction: Over 100, Then ReduceA percentage is just a fraction out of 100. Put the number over 100, reduce to lowest terms, and handle decimal percentages like 12.5% by clearing the decimal first. With examples.How-toHow to Calculate a Percentage: 4 Methods with ExamplesA clear guide to percentages: find X% of a number, work out what percent one number is of another, and add or subtract a percentage — with worked examples.How-toPercentage Change: Increase and DecreaseSubtract old from new, divide by the old value, times 100. Here's the formula, why increases and decreases aren't symmetric, and where it's used.