Aspect Ratio Calculator

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How Do I Find the Aspect Ratio of an Image?

Divide the width and the height by their greatest common divisor. A 1920 x 1080 image divides by 120 to give 16:9; a 1080 x 1350 post divides by 270 to give 4:5. Enter any size above and the calculator shows the ratio, the decimal value and the matching size at a new width or height, so the picture is never stretched.

How to use the calculator

1. Type the current width and height in pixels, or tap a platform size such as Instagram Portrait post.
2. Read the aspect ratio (for example 16:9) and its decimal value.
3. Type a new width to get the matching height, or a new height to get the width.

The Resize Formula

To keep the same shape, scale both sides by the same factor:

• New height = new width x original height ÷ original width
• New width = new height x original width ÷ original height

Worked example: a 1920 x 1080 video resized to 1280 px wide becomes 1280 x 1080 ÷ 1920 = 720 px high, so 1280 x 720, still 16:9. A 4:5 Instagram post made 1080 px wide needs 1080 x 5 ÷ 4 = 1350 px of height.

Social Media Image and Video Sizes (2026)

Recommended sizes in pixels, width x height. Platforms change these from time to time, so check the platform's own guidance if an upload looks cropped.

Source: recommended sizes compiled from Buffer's 2026 social media image size guide, checked October 2026.

Common Aspect Ratios Explained

Tips for Images That Don't Get Cropped

• Upload at the recommended size, not just the right ratio: a 400 x 500 image is 4:5 but looks soft when the platform scales it up.
• Keep text and faces in the centre. Stories and Reels put buttons along the bottom and right edges.
• Crop rather than stretch. If your photo is 3:2 and you need 4:5, crop the sides instead of squeezing it.
• Design once, export several sizes. A 1080 x 1350 design converts to 1080 x 1080 by trimming 270 px of height.

Writing captions or descriptions to go with the image? Check their length with the word counter, and fix capitals with the case converter.

Who Uses the Aspect Ratio Calculator?

• Social media managers: export one design at the right size for Instagram, Facebook, YouTube and LinkedIn.
• Video editors: resize 16:9 footage or set a 9:16 frame for Reels, Shorts and TikTok.
• Web designers and developers: set image width and height attributes that keep the right shape.
• Photographers: check how a 3:2 photo will crop for 4:5 or 1:1 posts.

How the Aspect Ratio Calculator Saves You Time

Finding the common divisor and doing the resize maths for every format by hand adds up when you post to several platforms. One tap on a platform size gives the ratio and pixels instantly.