Ratio Calculator
Simplify ratios to lowest terms. Scale to any target value. Convert to decimal or percent.
Type two values to get the simplified ratio. Optionally scale to a target value (e.g., resize 1920 wide while keeping the same aspect).
Simplify or scale a ratio
Scale to a target (optional)
Examples: 16:9 stays 16:9 (already simplified). 1920:1080 simplifies to 16:9. 4:8 simplifies to 1:2.
What a ratio actually is
A ratio expresses the relationship between two quantities. "16:9" means for every 16 units of the first, there are 9 units of the second. Ratios are simplified by dividing both sides by their greatest common factor (GCD). 1920:1080 simplifies to 16:9 by dividing both by 120.
Common ratio uses
- Screen aspect ratios: 16:9 (widescreen), 4:3 (older), 21:9 (ultrawide), 1:1 (square)
- Photography: 3:2 (DSLRs), 4:3 (phones), 1:1 (Instagram)
- Mixing ratios: paint to thinner (e.g., 4:1), fuel to oil (e.g., 50:1), drink mixes
- Map scales: 1:24,000 (1 inch on map = 24,000 inches on ground)
- Recipe scaling: if a recipe uses 2 cups flour to 1 cup sugar, you maintain 2:1 when scaling up
Scaling a ratio
Pick one side of the ratio and set its new value. The other side scales proportionally. If 16:9 needs to scale so the first side equals 1920, the second side automatically becomes 1080. This is useful for resizing images, scaling recipes, mixing chemicals at a different total volume, and any other proportion math.