Screen Ratio Calculator
This calculator works out the aspect ratio of any screen, image or video from its width and height in pixels, then shows you what a matching size looks like at a different resolution. Getting the ratio right matters when you are buying a monitor or TV, cropping a photo, setting up a video export, or checking whether a design will letterbox or stretch on a different screen. Enter the width and height in any consistent unit, or pick a common resolution from the preset list, and the calculator returns the simplified ratio (found using the greatest common divisor), the decimal ratio from dividing width by height, and the closest standard named ratio such as 16:9, 16:10, 4:3 or 21:9. A ratio breakdown shows the GCD, total pixel count and how close your dimensions sit to that named standard, alongside a simple visual box so you can see the shape at a glance. To resize while keeping the same proportions, switch to the scaling section and enter a target width, target height or scale factor; the calculator works out the matching dimension and lists common resolutions that share your ratio, flagging any exact match. Use it before ordering hardware, exporting video, or resizing images for a website or social platform, so you know how the proportions will look before you commit to a size.
1. Screen or Image Dimensions
2. Scale to a New Size
Ratio Breakdown
Scaled Dimensions
Common Resolutions at This Ratio
| Name | Width | Height | Total Pixels | Match? |
|---|
How to Calculate Screen Aspect Ratio
The aspect ratio of a screen or image is the proportional relationship between its width and height. It is expressed as two integers separated by a colon (such as 16:9) or as a single decimal number (such as 1.78).
To find the simplified aspect ratio from pixel dimensions:
- Find the greatest common divisor (GCD) of the width and the height using the Euclidean algorithm.
- Divide both the width and the height by the GCD.
- The result is the lowest integer ratio (for example, 1920 / 120 = 16 and 1080 / 120 = 9, giving 16:9).
For a decimal ratio, simply divide width by height: 1920 / 1080 = 1.7778.
Common Screen Ratios and Their Uses
| Ratio | Decimal | Common Resolutions | Typical Use |
|---|---|---|---|
| 16:9 | 1.778 | 1280x720, 1920x1080, 2560x1440, 3840x2160 | TVs, monitors, video content, most laptops |
| 16:10 (8:5) | 1.600 | 1280x800, 1920x1200, 2560x1600 | Productivity laptops, some tablets |
| 4:3 | 1.333 | 640x480, 800x600, 1024x768 | Older monitors, standard definition TV, tablets |
| 21:9 | 2.333 | 2560x1080, 3440x1440 | Ultrawide monitors, cinema |
| 32:9 | 3.556 | 3840x1080, 5120x1440 | Super ultrawide monitors |
| 1:1 | 1.000 | 1080x1080 | Social media square images |
| 9:16 | 0.563 | 1080x1920 | Vertical video (mobile), stories |
| 4:5 | 0.800 | 1080x1350 | Instagram portrait posts |
| 3:2 | 1.500 | 2160x1440 | Surface devices, some cameras |
| 5:4 | 1.250 | 1280x1024 | Older 17-19 inch CRT/LCD monitors |
Scaling While Preserving Aspect Ratio
To scale an image or resolution while keeping the same ratio:
- Given target width: height = target width / (original width / original height)
- Given target height: width = target height * (original width / original height)
- Given a scale factor: new width = original width * factor; new height = original height * factor
When scaling pixel dimensions, round to the nearest whole pixel. Some encoded video formats require dimensions that are multiples of 2 (or 4 or 8), so you may need to round to the nearest even number.
Worked Example
A 1920 x 1080 screen is the default input for this calculator. Here is how the ratio is derived:
- GCD(1920, 1080): 1920 = 1 x 1080 + 840; 1080 = 1 x 840 + 240; 840 = 3 x 240 + 120; 240 = 2 x 120 + 0. So GCD = 120.
- Simplified ratio: 1920 / 120 = 16; 1080 / 120 = 9. Ratio is 16:9.
- Decimal ratio: 1920 / 1080 = 1.7778.
- Scaling to width 1280: height = 1280 / (1920 / 1080) = 1280 / 1.7778 = 720. Result: 1280 x 720.
Related Calculators
- Maths and Stats Calculators: all maths and geometry tools.
- Aspect Ratio Calculator: resize dimensions to a given aspect ratio.
- Image Ratio Calculator: ratio calculations for images and graphics.
- Area of a Circle Calculator: geometry calculations.
- Circumference Calculator: circle circumference from radius or diameter.
Sources and method: Aspect ratio calculation uses the Euclidean algorithm for greatest common divisor. Standard ratio names follow display industry conventions (VESA, ISO, CEA-861). Closest standard ratio is determined by minimum absolute difference in decimal ratio from named standards.
Scaled dimensions are rounded to the nearest whole pixel. For video encoding, dimensions may need to be multiples of 2 or 4 depending on the codec. This calculator covers standard display ratios only; non-standard ratios may not have a widely recognised name.