Ratio Calculator
Simplify a ratio to lowest terms, solve a proportion for the missing value, or split any total amount by ratio — with a visual proportional bar and a fraction, decimal and percentage breakdown for every term.
⚡ Quick Tips for Working With Ratios Correctly
Features
Reduce any ratio to lowest whole-number terms, including decimal inputs like 2.5:5.
Leave one value blank to solve for it, or fill all four to check equivalence directly.
Divide rent, profit or ingredients into 2–4 parts, with parts guaranteed to sum to the total.
A proportional colored bar and legend make each term's share immediately visible.
Every simplified term shown as a reduced fraction, a decimal and a percentage at once.
Quick-fill buttons for 16:9, 4:3, 1:1, 21:9, 9:16 and 3:2 — the six most common screen ratios.
Why a Ratio Calculator Needs Three Modes, Not One
Most free ratio calculators do exactly one thing — simplify two numbers to lowest terms — which handles a homework problem but misses the two questions that come up just as often outside the classroom: "what value makes these two ratios equal?" and "how do I actually divide this amount according to a ratio?" All three are the same underlying idea, just pointed at different problems, which is why this tool treats simplifying, solving and splitting as equally central rather than making splitting an afterthought bolted onto a basic simplifier.
Take 1920:1080, a screen resolution most people have seen without necessarily recognizing it as a ratio. Simplify Ratio mode reduces it to 16:9 by dividing both terms by their greatest common divisor, 120 — the same GCD-based method used for any two-term ratio, aspect ratio or otherwise. Change the question slightly — "if a screen is 16:9 and 1,600 pixels wide, how tall is it?" — and that's now a proportion: 16:9 = 1600:?, solved by cross multiplication in Solve Proportion mode instead.
The Fraction-Decimal-Percentage Breakdown, Explained
A simplified ratio like 1:3 tells you the relationship between two quantities, but it doesn't say outright what share of the whole each part represents — that takes one more step most calculators skip. This tool computes it automatically: term 1 is 1/4 of the total (25%), term 2 is 3/4 (75%). The fraction shown for each term is independently reduced to its own lowest form rather than just dividing by the ratio's overall GCD, since a term-to-sum fraction can simplify further even after the ratio itself is fully reduced — 2 out of a sum of 6 reduces to 1/3, even though the ratio 2:4 (say) had already been simplified to 1:2 beforehand.
Ratios, Odds and Probability Aren't Quite the Same Thing
A ratio like 3:5 simply compares two quantities against each other — no implication of chance is involved. Odds, used in betting and risk contexts, compare an event happening against it not happening (3:5 odds means 3 favorable outcomes for every 5 unfavorable ones), while probability expresses the favorable outcomes as a share of every possible outcome — that same situation as a probability is 3-in-8, or 37.5%, not 3-in-5. Mixing these up is a common source of misread statistics, since a news headline stating "odds of 1:4" and "a 1-in-4 chance" describe genuinely different likelihoods once converted properly. For calculations that are actually about chance rather than a plain comparison of two quantities, the Probability Calculator handles that distinction directly.
Who Actually Reaches for a Ratio Calculator
Students checking ratio and proportion homework across simplifying, solving and real-world word problems, not just the simplification step most lessons start with. Cooks and bakers scaling a recipe written for four servings up to eight, or splitting a batch of dough by a flour-to-water-to-yeast ratio for a different total weight. Small business partners dividing profit or expenses by an agreed ratio rather than an even split, where Split a Total mode turns an ownership ratio directly into dollar amounts. Designers and video editors confirming a crop or export matches a required aspect ratio before delivery, using the same simplification logic as any other two-term ratio. For percentage-only calculations that don't involve a second quantity to compare against, the Percentage Calculator is the more direct tool.
Two Calculations Worth Walking Through
Recipe scaling: a bread recipe uses flour, water and yeast in a 5:3:1 ratio by weight. Scaling it to a 900-gram dough total means dividing 900 across those three parts by their combined ratio of 9: flour gets 5/9 × 900 = 500 g, water gets 3/9 × 900 = 300 g, and yeast gets 1/9 × 900 = 100 g — three numbers that add back to exactly 900 g, computed directly in Split a Total mode without doing the arithmetic by hand.
Map-scale proportion: a map states a scale of 1:50,000, meaning 1 cm on paper represents 50,000 cm (500 m) in reality. Measuring a 3.4 cm distance between two towns turns into the proportion 1:50,000 = 3.4:?, solved by cross multiplication for a real-world distance of 170,000 cm, or 1.7 km — the exact same mechanism as solving for any other missing proportion term.
Both examples share the same underlying shortcut: once one full ratio is known and only a single value in the second is missing, cross multiplication turns what looks like an algebra problem into a single multiplication and division. Nothing about the method changes whether the ratio describes grams of flour, centimeters on a map, or dollars in a partnership — the same A × D = B × C relationship solves all of them identically.
Why Browser-Based Beats Manual Cross Multiplication
Simplifying a four-term ratio or checking equivalence by hand means finding a greatest common divisor across several numbers at once, which gets error-prone quickly past two terms. This tool runs every GCD reduction, cross multiplication and split calculation entirely client-side in JavaScript, with nothing entered ever transmitted to a server — safe for confidential business splits or coursework kept private. For fraction arithmetic beyond ratio simplification — adding, subtracting or comparing fractions directly — the Fraction Calculator handles that on its own.
Where This Calculator Draws the Line
It simplifies, solves and splits ratios of up to four terms — it doesn't handle continued ratios with variable unknowns in multiple positions at once, ratio-based statistical measures like odds ratios in epidemiology, or unit conversion between different measurement systems. For converting a ratio's units before comparing it — feet to meters, for instance — the Length Converter handles that conversion step first.