Ratio & Proportion Calculator
Use our free online Ratio Calculator to perform fast, accurate calculations with instant formulas, step-by-step arithmetic, and verified reference benchmarks.
Ratio Calculator
Instant Live Computation • Zero Waiting
Adjust inputs on the left for instantaneous live computation.
How to Calculate: The Ratio Calculator Formula
Solves for any single unknown variable (A, B, C, or D) using cross-multiplication, and reduces ratios using greatest common divisors.
Step-by-Step Calculation Guide
- Input known values in proportion A : B = C : D.
- Leave unknown field blank to solve.
- Review simplified ratio format (1 : n and n : 1).
- Inspect equivalent percentage and decimal multiplier.
Practical Ratio Calculator Examples
Original recipe uses 2 cups flour to 3 cups sugar (2:3). How much sugar is needed for 6 cups of flour?
16:9 video scaled to 1080px height. What is the width?
Common Aspect Ratios and Dimensions
Official reference values and benchmark classifications based on standard institutional guidelines.
| Ratio Format | Common Use Case | Decimal Equivalent | Normalized (1 : n) |
|---|---|---|---|
| 1 : 1 | Square (Instagram posts, profile photos) | 1.000 | 1 : 1.00 |
| 4 : 3 | Classic TV, iPad screens, photography | 1.333 | 1 : 0.75 |
| 16 : 9 | Widescreen HD video, YouTube, monitors | 1.777 | 1 : 0.56 |
| 21 : 9 | Ultrawide gaming monitors, cinematic film | 2.333 | 1 : 0.43 |
| 9 : 16 | Vertical video (TikTok, Instagram Reels, Shorts) | 0.562 | 1 : 1.78 |
Frequently Asked Questions about Ratio Calculator
How do you simplify a ratio?
Divide both numbers by their Greatest Common Divisor (e.g. 12:18 divides by 6 to simplify to 2:3).
What is the difference between a ratio and a fraction?
A ratio compares two parts to each other (part-to-part, e.g. 2 boys to 3 girls). A fraction compares a part to the whole total (part-to-whole, e.g. 2 boys out of 5 children total = 2/5).
What is the Golden Ratio?
The Golden Ratio (phi, φ) is approximately 1.6180339887..., an aesthetically pleasing proportion found widely in nature, architecture, and classical art.
How do you scale a ratio up or down?
Multiply or divide all terms in the ratio by the same non-zero scaling factor.