Aspect ratio calculator for every size you need

Pick a ratio and type one side to get the other, or type a width and height to get the ratio. Answers update as you type.

Free, no sign upExact pixelsEven numbers for videoCrop percentage

Find the size for a ratio

Ratio
I know the
1080 by 1350

4:5 at 1080 wide.

Find the ratio of a size

by
16:9

1.778:1. This is exactly 16:9.

Cropping to 4:5 from
45%

A centred crop from 16:9 to 4:5 keeps 45% of the width. Blur fill or bars keep the whole picture instead.

Need the video itself in that shape? Resize it free in your browser.

How it works

  1. Step 1

    Choose a ratio

    Tap a common one such as 4:5 or 9:16, or type any ratio like 5:4 or 2.35:1.

  2. Step 2

    Type the side you know

    Width or height in pixels. The other side appears instantly, rounded to even numbers for video if you want.

  3. Step 3

    Check the crop

    See how much of a 16:9 or 9:16 source a centred crop to your ratio keeps before you edit.

Common aspect ratios in pixels

Widths across the top, heights rounded to even numbers so every size works as video.

Ratio720 wide1080 wide1440 wide2160 wideUsed for
9:16720 by 12801080 by 19201440 by 25602160 by 3840Reels, Shorts, TikTok, Stories
4:5720 by 9001080 by 13501440 by 18002160 by 2700Instagram and Facebook feed posts
1:1720 by 7201080 by 10801440 by 14402160 by 2160Square posts
16:9720 by 4061080 by 6081440 by 8102160 by 1216YouTube, TV, presentations
4:3720 by 5401080 by 8101440 by 10802160 by 1620Older video, many tablets
3:4720 by 9601080 by 14401440 by 19202160 by 2880Portrait photos
2:3720 by 10801080 by 16201440 by 21602160 by 3240Pins and portrait prints
21:9720 by 3081080 by 4621440 by 6182160 by 926Cinematic widescreen

How to calculate an aspect ratio

To find a height from a width, multiply the width by the second number of the ratio and divide by the first: 4:5 at 1080 wide is 1080 × 5 ÷ 4 = 1350. To find the ratio of a size, divide both sides by their greatest common divisor: 1920 by 1080 divides by 120 into 16:9.

Video encoders usually need even dimensions, so round to the nearest even number. The calculator does this when the box is ticked.

Which ratio the platforms accept

Checked on each platform’s own help pages. To turn a video into the ratio you picked, use the free video resizer.

  • Instagram accepts reels at any ratio from 1.91:1 to 9:16, at least 720 pixels and 30 frames a second.
  • YouTube calls 16:9 the standard on a computer, and treats uploads that are square or vertical and up to three minutes long as Shorts.
  • Facebook supports video from 16:9 to 9:16.

Platform facts checked on 17 September 2026 against each platform's own help pages.

Use it from an AI assistant or a script

Every setting is a URL parameter, so an assistant can send a link with the options already chosen. The tool still runs on the person's own device.

ParameterValuesDefaultMeaning
ratioany ratio, for example 4:5, 9:16, 16:9, 2.35:14:5The ratio to size.
width1 to 163841080Known width in pixels; the height is calculated.
height1 to 16384Known height in pixels, instead of width; the width is calculated.
w1 to 163841920Width of a size whose ratio you want (use with h).
h1 to 163841080Height of a size whose ratio you want (use with w).
from16:9, 9:16, 4:3, 1:1, 4:516:9Source ratio for the crop percentage.

Every free tool and its parameters, as JSON: percify.io/tools.json

More free tools

Video resizer

Choose a video, pick a shape and a fit, and download the result. Your file never leaves your device.

Generate video in the right shape from the start

Percify’s video models let you pick 9:16, 16:9 or 1:1 before generating, so nothing needs cropping afterwards.

Open the video models

Free to start · no credit card

Frequently asked questions

Everything you need to know before you start.

1080 by 1350 at 1080 wide, the usual size for Instagram and Facebook feed posts. Larger sizes are 1440 by 1800 and 2160 by 2700.

1080 by 1920 at 1080 wide, the size for Reels, Shorts and TikTok. Smaller is 720 by 1280; 4K vertical is 2160 by 3840.

16:9. Divide both sides by 120, their greatest common divisor, and you get 16 by 9.

Multiply the width by the second number of the ratio and divide by the first. For 4:5 at 1080 wide: 1080 × 5 ÷ 4 = 1350.

About 32% of the width. Cropping 16:9 to 4:5 keeps 45%, and to 1:1 keeps 56%. Blur fill or bars keep the whole picture instead.

Yes. The common sizes are in the table on this page, and a link such as /tool/aspect-ratio-calculator?ratio=4:5&width=1080 opens the calculator with the numbers filled in. /tools.json lists every parameter.