Aspect Ratios Explained: 16:9, 4:3, 3:2 and 1:1
What aspect ratios mean, which ones cameras, screens and social apps use, and how to calculate a new width or height without stretching an image.
By the CalClu team2 min read
An aspect ratio is the relationship between an image's width and height. It's written as width:height, and it decides how a photo or video fits on a screen.
Common ratios
- 16:9: HD and 4K video, most TVs and monitors
- 4:3: many smartphone photos, older TVs and Micro Four Thirds cameras
- 3:2: most DSLR and mirrorless cameras with APS-C or full-frame sensors (the shape of 35 mm film)
- 1:1: square
- 9:16: vertical video for phone-first apps
- 21:9 (approximately): ultra-wide monitors and cinema-style video
Finding a ratio from pixels
Divide the width and height by their greatest common divisor. 1920 × 1080 both divide by 120, giving 16:9. 6000 × 4000 divides by 2000, giving 3:2.
Resizing without stretching
Keep the ratio the same by solving a proportion:
To make a 3:2 photo 1,200 pixels wide: 1,200 × 2 ÷ 3 = 800 pixels tall. For 16:9 video at 1,280 pixels wide: 1,280 × 9 ÷ 16 = 720, the familiar 720p.
Cropping to a new ratio
Changing the ratio means cropping or adding bars. Going from 3:2 to 1:1 on a 6000 × 4000 image keeps a 4000 × 4000 square and discards a third of the width.
Pixels add up quickly
Doubling both the width and the height quadruples the number of pixels. A 4K frame (3840 × 2160) has four times the pixels of a 1080p frame (1920 × 1080), which is why 4K files are so much larger at similar quality.
Print sizes
A 3:2 image fits a 6 × 4 inch print perfectly, but an 8 × 10 print (4:5) needs cropping. Check the print ratio before you order.
Try the calculators
More tools in this area: Photography & Video calculators