Free calculator · no sign-up

Aspect Ratio Calculator Find the ratio or the missing side

Enter a width and height to get the ratio, or enter a ratio and one side to get the other. Works for screens, photos and video.

Reduces exactly with the greatest common divisor
Names the closest common screen ratio
Fit-into-a-frame mode shows bars or crop before you resize

Built by Marcus Reed, laptop and desktop repair technician

Aspect ratio calculatorratio = width ÷ height

What do you need?

WidthPixels or any unit

HeightSame unit as width

Example

Aspect ratio

–

Ratios are reduced exactly with the greatest common divisor, then matched to the nearest common screen ratio.

16:91920 × 1080, 2560 × 1440, 3840 × 2160
16:101920 × 1200, a taller work screen
64:27what a 2560 × 1080 ultrawide really is
4:31024 × 768 and many tablets

Quick answer

An aspect ratio is a screen or image’s width divided by its height, reduced to the smallest whole numbers. 1920 x 1080 is 16:9, 1920 x 1200 is 16:10 and 1024 x 768 is 4:3. Enter a resolution in the calculator above to get its ratio, or switch modes to find a missing width or height for a ratio you need to keep.

01 / 06

How the ratio is worked out

The calculator divides both numbers by their greatest common divisor. 2560 and 1440 share 160, which leaves 16 and 9, so 2560 x 1440 is 16:9. When a size doesn’t reduce to a familiar pair, the result also shows the ratio as a decimal and the closest common screen ratio.

02 / 06

Common aspect ratios and resolutions

Ratio	Decimal	Example resolutions	Where you see it
16:9	1.78	1920 × 1080, 2560 × 1440, 3840 × 2160	TVs, most monitors, video
16:10	1.6	1920 × 1200, 2560 × 1600	Many laptops and work monitors
3:2	1.5	2160 × 1440, 3000 × 2000	Some laptops and 2-in-1 tablets
4:3	1.33	1024 × 768, 1600 × 1200	Older monitors, many tablets
21:9 class	about 2.37 to 2.39	2560 × 1080, 3440 × 1440	Ultrawide monitors
32:9	3.56	3840 × 1080, 5120 × 1440	Super-ultrawide monitors
9:16	0.56	1080 × 1920	Phone screens held upright, vertical video

03 / 06

Using the ratio when you buy a screen

Diagonal size alone hides a lot. A 27-inch 16:9 monitor and a 34-inch 21:9 ultrawide are about the same height, so the ultrawide mostly adds width. For spreadsheets and documents, a taller 16:10 or 3:2 screen shows more rows at the same width. Sharpness is a separate question that depends on both resolution and size, and the PPI calculator answers it. What to look for when buying a laptop covers the rest of the screen checklist.

04 / 06

Cameras, apps and print sizes each have a native shape, and a mismatch is why photos get cropped. Instagram is the one that changed recently. Its Help Center describes feed photos between 1.91:1 landscape and 4:5 portrait, kept at up to 1080 pixels wide. Since 2025 the app also takes taller 3:4 feed posts at 1080 × 1440, matching the 3:4 tiles of the profile grid; Instagram head Adam Mosseri announced the change in May 2025. Not every tool has caught up: a 2026 r/Instagram post reports Meta Business Suite still warning that anything taller than 4:5 will be cropped.

Use	Ratio	Size
Instagram, tallest feed post	3:4	1080 × 1440
Instagram, portrait feed post (older limit)	4:5	1080 × 1350
Instagram, square post	1:1	1080 × 1080
Instagram, widest landscape post	1.91:1	1080 × 566
Vertical video and phone screens held upright	9:16	1080 × 1920
Widescreen video	16:9	1920 × 1080 (1080p)
4 × 6 inch print	3:2	Same shape as most camera sensors
8 × 10 inch print	4:5	Crops the long side of a 3:2 photo

A typical phone photo is 4:3 (4032 × 3024), or 3:4 when taken upright, which is exactly the new tallest Instagram shape, so upright phone photos can post without a crop. Camera photos are usually 3:2, and that is the classic print trap. As one r/photography reply put it, a 3:2 image printed as-is at 8 × 10 is “going to lose the top/bottom”. Use the Missing side mode to plan the crop before you order: enter 4 and 5 as the ratio and the photo’s short side to see what you keep. Instagram’s own wording is on its Help Center page on photo resolution.

05 / 06

Fitting one shape inside another

When a picture and a screen have different ratios, there are only two choices: shrink the picture until it fits and accept bars, or enlarge it until it fills and accept a crop. The Fit into a frame mode does both calculations. Three examples:

Picture	Frame	Fit with bars	Crop to fill keeps
4:3 phone photo, 4032 × 3024	1920 × 1080 slide or TV	1440 × 1080, bars of 240 px left and right	75% of the photo
2.39:1 film, 1920 × 803	1920 × 1080 TV	1920 × 803, bars of about 139 px above and below	74.4% of the film
16:9 video, 1920 × 1080	1080 × 1920 phone, upright	1080 × 608, bars of 656 px above and below	31.6% of the video

For slides and photo frames, fitting with bars keeps the whole picture. For a phone wallpaper or a vertical video, cropping usually looks better, but plan what sits in the middle third of the frame, because that is all a 16:9 shot keeps on an upright phone.

06 / 06

Black bars and stretched video

When video and screen ratios differ, the player adds black bars or crops, and stretching to fill distorts the picture. A 16:9 video on a 16:10 laptop shows thin bars above and below; a 21:9 film on a 16:9 TV shows thicker ones. If a game or desktop looks stretched, set the resolution in display settings to one that matches the screen’s native ratio, usually the one Windows marks as recommended.

FAQ

Questions people ask

What aspect ratio is 1920 x 1080?

16:9. 1920 and 1080 share a greatest common divisor of 120, and 1920 divided by 120 is 16 while 1080 divided by 120 is 9.

Is 2560 x 1080 really 21:9?

Not exactly. 2560 x 1080 reduces to 64:27, about 2.37:1, and 3440 x 1440 reduces to 43:18, about 2.39:1. Both are sold as 21:9, which is 2.33:1. The label is a family name rather than the exact math.

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

A 16:10 screen is taller for the same width: 1920 x 1200 instead of 1920 x 1080. The extra 120 rows show more of a document or web page, which is the main reason to pick 16:10 for work.

How do I resize an image without stretching it?

Keep the ratio fixed and change one side. Use the Missing side mode: enter the original ratio, type the new width, and the calculator gives the matching height.

All calculators