Free tool
Aspect Ratio Calculator
Turn any width and height into its ratio, work out the missing side of a resize, and see how much of a photo a crop to 4:5, 16:9 or an 8 × 10 print will cost you.
Nothing is uploaded. Everything is calculated in your own browser, including any photo you choose to check. There is no signup and no account.
Find the ratio of any size
Type a width and height in pixels, inches or centimetres — any unit, as long as both match.
Resize to a ratio
Pick or type a ratio, then enter either side. The other one is worked out for you.
Common ratios
Print sizes
Social formats
Platform sizes come from Instagram Help, Meta’s Ads Guide and YouTube Help, checked in October 2026. Platforms change these; check before a big batch.
Check a photo against a ratio
Choose a photo to read its size and see what a crop to another ratio would remove. The photo stays on your device.
How to use it
- To find a ratio, type the width and height. 6000 × 4000 gives 3:2; 1080 × 1350 gives 4:5.
- To resize, pick a ratio and type the side you know. A 16:9 frame 1920 wide is 1080 tall.
- To plan a crop, choose a photo and a target. The dimmed area is what a centred crop removes.
What the ratio means for a photographer
An aspect ratio is a shape, not a size. A 3:2 frame is one and a half times as wide as it is tall whether it is 3000 or 6000 pixels across. That is why a ratio alone cannot tell you how large a photo will print — the pixel count decides that.
The ratio matters the moment the photo has to fit a different shape. A 3:2 camera file fills a 4 × 6 print exactly, but an 8 × 10 is 4:5, so about a sixth of the long side has to go. Knowing that before the shoot is the reason to leave space around the subject.
For the size side of the question, use the megapixel calculator or the print size checker.
Aspect ratios
Frequently asked questions
What is an aspect ratio?
The proportion between an image’s width and its height, written width:height. A 6000 × 4000 photo is 3:2. It describes the shape only: 3000 × 2000 is also 3:2.
What aspect ratio do cameras shoot?
Most DSLR and mirrorless cameras with APS-C or full-frame sensors shoot 3:2. Micro Four Thirds cameras and most phones shoot 4:3 by default. Many cameras can also record 1:1 or 16:9 by cropping the sensor.
Why does an 8 × 10 print crop my photo when a 4 × 6 does not?
A 4 × 6 print is 2:3, the same shape as a 3:2 camera file, so nothing is lost. An 8 × 10 is 4:5, which is squarer, so a centred crop removes about 16.7% of the frame from the long side.
Which ratio should I use for Instagram?
Meta’s documentation allows feed photos between 4:5 portrait and 1.91:1 landscape, and its Ads Guide recommends 1440 × 1800 pixels at 4:5. Stories and Reels are 9:16, recommended at 1440 × 2560.
Does changing the aspect ratio lower the quality?
Cropping does not soften the pixels that remain, but it leaves fewer of them, so the photo prints smaller at the same sharpness. Changing the ratio without cropping stretches the picture, which is never what you want.