How do I calculate the aspect ratio of a screen from its width and height?

Divide both the width and height by their greatest common divisor (GCD). For example, a 1920 x 1080 screen: GCD(1920, 1080) = 120, so 1920 / 120 = 16 and 1080 / 120 = 9, giving an aspect ratio of 16:9. For a decimal ratio, simply divide width by height: 1920 / 1080 = 1.778.

What is the difference between 16:9 and 16:10?

16:9 is the dominant widescreen standard used for televisions, most monitors, and video content. It has a decimal ratio of approximately 1.778. 16:10 (also written 8:5) is slightly taller and was common on laptop screens and older monitors. A 1920 x 1200 display is 16:10 and provides more vertical space for productivity work. 16:10 screens are experiencing a revival in laptops as users prefer the extra vertical height for documents and web pages.

How do I scale a resolution while keeping the same aspect ratio?

Multiply both width and height by the same scale factor, or use the ratio to solve for the missing dimension. If you know the target width, calculate target height = target width divided by (original width divided by original height). If you know the target height, calculate target width = target height multiplied by (original width divided by original height). This calculator does this automatically when you enter a target width or height in the scaling section.

Screen Ratio Calculator

Enter the width and height of any screen, image, or video in pixels (or any consistent unit) to find the exact aspect ratio, simplified ratio, and closest standard ratio. Use the scaling section to find the width or height for a different size at the same ratio.

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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

Width (pixels or any unit)

Height (pixels or any unit)

Quick preset (optional)

2. Scale to a New Size

Scale by

Target width

Target height

Scale factor (e.g. 0.5 = half size, 2 = double)

Aspect Ratio Results

Simplified Ratio
16:9
Exact integer ratio

Decimal Ratio

1.778

Width / Height

Closest Standard

16:9

Named ratio

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

Closest named ratio16:9 (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

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.
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.

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