Enter any ratio and solve for the missing value, simplify it, or scale it up and down
Handles A:B = C:D proportions, multi-part ratios like 2:3:5, and...
Divide both sides of the ratio by their greatest common divisor (GCD). For example, 12:18 simplifies to 2:3 by dividing both by 6. In General mode, pick Simplify — the calculator reduces any whole-number or decimal ratio to its lowest terms and shows the GCD.
Multiply both terms by the same number. For example, 2:3 scaled by 4 becomes 8:12, which is equivalent because it keeps the same value. The Scale task scales by any factor and shows an equivalent-ratio table (1×, 2×, 3×, 4×, 5×, 10×).
Use cross-multiplication. If A:B = C:x, then A×x = B×C, so x = (B×C) / A. Enter three known values in the Solve task and the calculator finds the fourth automatically — for example, 2:3 = 8:x gives x = 12.
Cross-multiply: A:B equals C:D when A×D = B×C. For example, 4:6 and 2:3 are equivalent because 4×3 = 6×2 = 12. The Compare task does this for you and tells you whether the two ratios are equivalent.
A ratio A:B is the fraction A/B. Divide to get the decimal (3:2 = 1.5), multiply by 100 for the percent (150%), or use A/(A+B) and B/(A+B) for each part’s share of the whole (60% and 40%). The Convert task shows all of these at once.
A part-to-part ratio compares two parts to each other (e.g., 2:3 boys to girls). A part-to-whole ratio compares one part to the total (e.g., 2 out of 5, or 40%). The Convert task’s share-of-total output turns a part-to-part ratio into part-to-whole percentages.
A ratio compares two quantities (e.g., 3:4). A proportion states that two ratios are equal (e.g., 3:4 = 6:8). Use the Solve task to find a missing value when one ratio is known and the other is partially known.
Add all parts (2+3+5=10), then divide the total by 10 to get one part, and multiply by each ratio number. For example, splitting $100 in a 2:3:5 ratio gives $20, $30, and $50. Use Split mode to do this for any number of parts.
CalcTrail is a comprehensive free online calculator platform offering a comprehensive collection of specialized calculators for finance, health, academics, engineering, AI tools, and more. All calculators are free to use with no sign-up required. Create an account to save your work, access unlimited calculation history, workspace management, and custom variables.
This calculator is part of CalcTrail's collection of professional-grade tools designed for students, professionals, and anyone who needs accurate calculations. Export your results to PDF, JSON, or CSV formats. All calculations are performed client-side for privacy and speed.
Browse all calculators on CalcTrail to discover more tools for your needs.
Ratio Calculator
Calculate mixing ratios and mechanical ratios (pulleys/gears).