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Ratio Calculator
Simplify, scale, and solve ratios and proportions instantly.
Simplify Any Ratio
Reduce to the simplest form using GCD
Scale & Solve
Find missing values in proportions
Percentage & Fraction
Convert ratios to percentages and fractions
Calculate Ratios
Simplify, scale, or solve ratios and proportions.
How to Simplify and Scale Ratios
The GCD Method
Simplified = A÷GCD(A,B) : B÷GCD(A,B)
Example: 24:16 → GCD=8 → 3:2
The greatest common divisor (GCD) is the largest number that divides both A and B evenly. Dividing both sides by the GCD gives you the simplest form — no further reduction is possible.
Scaling & Solving
To scale a ratio, multiply both parts by the same factor. To solve A:B = C:?, use cross-multiplication: ? = B×C÷A. For example, if 3:5 = 12:?, then ? = 5×12÷3 = 20. This works for any proportional relationship — recipes, maps, or financial ratios.
Ratios in Finance and Business
Financial Ratios
Price-to-earnings (P/E), debt-to-equity, and current ratio are essential for analysing companies. A P/E of 15 means investors pay £15 for every £1 of earnings. Debt-to-equity compares how much a company owes versus what shareholders own — lower is generally safer.
Portfolio Ratios
Asset allocation ratios guide portfolio construction. A 60:40 stock-to-bond split is a classic balanced portfolio. Risk-reward ratios in trading (e.g. 1:3 risk-to-reward) ensure potential profits exceed potential losses before entering a position.
How to Use This Ratio Calculator
Choose a Mode
Simplify, scale, or solve a proportion.
Enter Values
Type your ratio values A and B, plus a target if scaling or solving.
View Results
See simplified form, equivalents, and percentage conversions.
Understanding Ratio Types
- Part-to-part. Compares one part of a whole to another — e.g. 3 boys to 5 girls (3:5). Both sides refer to subsets of the total.
- Part-to-whole. Compares a part to the total — e.g. 3 out of 8 students (3:8). This is essentially a fraction and converts directly to a percentage (37.5%).
- Rates. A special ratio comparing different units — e.g. miles per hour, price per unit, or earnings per share. Unlike pure ratios, rates have units.
- Proportions. An equation stating two ratios are equal — e.g. 2:3 = 4:6. Cross-multiplication lets you solve for any missing value.
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