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.
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Standard ratios as at 2026
Covers 16:9, 16:10, 4:3, 21:9, 32:9 and other common display standards.
1. Screen or Image Dimensions
px
px
2. Scale to a New Size
px
px
x
Aspect Ratio Results
Simplified Ratio
16:9
GCD = 120
Decimal Ratio
1.7778
Width / Height
Closest Standard
16:9
Exact match
Scaled Dimensions
1280 x 720
At target size
16:9
Visual representation of ratio (not to screen scale)
Ratio Breakdown
Input width1,920 px
Input height1,080 px
Greatest common divisor120
Simplified ratio (W:H)16:9
Decimal ratio (W/H)1.7778
Total pixels2,073,600 px
Closest named ratio16:9 (Widescreen) (exact match)
Scaled Dimensions
Scale modeBy target width
Target input1,280 px
Scale factor applied0.6667x
Scaled width1,280 px
Scaled height720 px
Scaled pixels (total)921,600 px
Scaled dimensions1280 x 720
Common Resolutions at This Ratio
Name
Width
Height
Total Pixels
Match?
Result:Enter dimensions above to see results.
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.
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.
