Aspect Ratio Calculator
The aspect ratio of a width and height in lowest terms, such as 16:9, or the missing side when you resize an image or screen and keep its shape.
Result
Aspect ratio: 16:9
Exact for the sizes typed; only the resized side is rounded for display.
- Width ÷ height
- 1.7778
https://calcgallery.com/everyday-math/aspect-ratio-calculator/
Results follow the mathematical operation and values shown. Check that you selected the intended operation, convention and dataset type before relying on the result. Read the full disclaimer
How to use the Aspect Ratio Calculator
- Choose whether you want the ratio itself, or the new height or width after a resize.
- Enter the original width and height, in pixels or any one unit.
- For a resize, enter the new width or height, and read the other side that keeps the same shape.
The formula
An aspect ratio is the width compared with the height, written in lowest whole terms:
ratio = (W ÷ g) : (H ÷ g), where g = gcd(W, H)new height = new width × H ÷ Wnew width = new height × W ÷ HThe resize lines are one proportion, new width ÷ new height = W ÷ H, solved by cross-multiplying for whichever side is missing.
Decimals and the decimal form
A decimal side is read exactly as typed, so a cinema frame of 2.39 by 1 is 239:100. The width ÷ height line gives the same shape as one number, the way lenses and film formats are often quoted: 16:9 is 1.7778, and 4:3 is 1.3333.
Screens
The same ratio sets a screen’s shape. To turn a ratio and a diagonal into a width and height, use the screen size calculator; to find how densely the pixels are packed, use the PPI calculator.
With your numbers
- 1,920 : 1,080 = 16:9 in lowest terms
Quick reference
Exact for the sizes typed; only the resized side is rounded for display.
| Example | Result |
|---|---|
| 1920 × 1080 | Aspect ratio: 16:9 |
| 1280 × 1024 | Aspect ratio: 5:4 |
| 2560 × 1080 | Aspect ratio: 64:27 |
| 1366 × 768 | Aspect ratio: 683:384 |
| 6000 × 4000 photo | Aspect ratio: 3:2 |
| 1920 × 1080 to 1280 wide | New height: 720 |
| 1024 × 768 to 1080 high | New width: 1,440 |
| 6000 × 4000 to 1000 wide | New height: 666.67 |
Common questions about the Aspect Ratio Calculator
- How do I work out an aspect ratio?
- Divide the width and the height by their greatest common factor. For 1920 by 1080 that factor is 120, which leaves 16 and 9, so the ratio is 16:9. The ratio has no unit: a 16:9 picture is 16:9 in pixels, inches or centimetres.
- How do I resize an image without stretching it?
- Keep width ÷ height the same. Multiply the new width by the original height and divide by the original width: 1280 × 1080 ÷ 1920 = 720, so a 1920 × 1080 image scaled to 1280 wide is 720 high.
- Why is my ratio not a round number like 21:9?
- Because the pixel counts do not reduce that far. 2560 × 1080 is exactly 64:27, about 2.37 to 1. Names such as 21:9 are round labels for a family of close shapes, not exact ratios, and 1366 × 768 is likewise 683:384 rather than exactly 16:9.
- What if the new size comes out as a fraction?
- Pixels come whole, so round it. A 6000 × 4000 photo scaled to 1000 wide is 666.67 high; 667 is the nearest whole pixel, and the page says when rounding like this moves the shape very slightly off the original.