Aspect Ratio Calculator

Aspect ratio is width divided by height, shown as the smallest whole numbers: divide both sides by their greatest common divisor, so 1920 × 1080 reduces to 16:9. To resize without distortion, keep the ratio fixed: new height = new width × (ratio height ÷ ratio width).

Published · Updated · Sources last verified

Find the ratio of a size

Type a width and height in pixels.

The size is read in your browser; the file is never uploaded.

Aspect ratio 16:9 (1.778:1). Exact match for 16:9.

Aspect ratio

16:9

1.778:1

Exact match for 16:9.

Width ÷ height
1.7778
Height ÷ width
0.5625
Shape
landscape

Your numbers, worked

gcd(1920, 1080) = 120

1920 ÷ 120 = 16

1080 ÷ 120 = 9

1920 ÷ 1080 = 1.7778

Show how the gcd was found
  1. 1920 = 1 × 1080 + 840
  2. 1080 = 1 × 840 + 240
  3. 840 = 3 × 240 + 120
  4. 240 = 2 × 120 + 0

Divide the larger side by the smaller, then divide the last divisor by the remainder until the remainder is 0. The last divisor is the gcd.

What each ratio would cut from 1920 × 1080

The largest centred crop at each ratio, best fit first. Crop rather than stretch.

RatioFitCrop toLost
16:9Exact1920 × 10800%
1.91:1Trim height1920 × 10056.94%
16:10Trim width1728 × 108010%
2:1Trim height1920 × 96011.1%
3:2Trim width1620 × 108015.6%
21:9Trim height1920 × 82323.8%
4:3Trim width1440 × 108025%
5:4Trim width1350 × 108029.7%
1:1Trim width1080 × 108043.8%
32:9Trim height1920 × 54050%
4:5Trim width864 × 108055%
3:4Trim width810 × 108057.8%
2:3Trim width720 × 108062.5%
9:16Trim width608 × 108068.3%

Solve the missing side

Pick a ratio, then enter the side you know.

Side you know

Height is 720. Size 1280 by 720 pixels.

Size at 16:9

1280 × 720

Height solved, in pixels.

Your numbers, worked

H = W × 9 ÷ 16 = 1280 × 9 ÷ 16 = 720

Whole number, so no rounding is needed.

Pixel-exact: a 16:9 size needs the width to be a multiple of 16, and 1280 is 80 × 16.

How to work out an aspect ratio by hand

There are two methods, and they answer slightly different questions. The divisor method gives the exact whole-number ratio. The decimal method tells you how close a size is to a named ratio such as 16:9.

Method 1: divide by the greatest common divisor

Find the largest number that divides both sides, then divide each side by it. Euclid’s algorithm finds that number with a few divisions. For 1920 × 1080: 1920 ÷ 1080 leaves 840, 1080 ÷ 840 leaves 240, 840 ÷ 240 leaves 120, and 240 ÷ 120 leaves 0. The last divisor, 120, is the greatest common divisor. Then 1920 ÷ 120 = 16 and 1080 ÷ 120 = 9, so the ratio is 16:9.

Method 2: divide width by height

1920 ÷ 1080 = 1.778, and 16 ÷ 9 is also 1.778, so the two match. This is the faster check when a size is near a named ratio but you are not sure it is exactly on it.

Redo these yourself

  • 1080 × 1350: 1350 ÷ 1080 leaves 270, and 1080 ÷ 270 leaves 0, so the divisor is 270. 1080 ÷ 270 = 4 and 1350 ÷ 270 = 5. The ratio is 4:5 (0.8).
  • 1080 × 1920: divisor 120, ratio 9:16 (0.5625). It is the 1920 × 1080 frame turned upright.
  • 1200 × 628: divisor 4, ratio 300:157 (1.9108). Nobody says “300:157”. The size is called 1.91:1 because 1200 ÷ 628 rounds to 1.91.
  • 1920 × 1000: divisor 40, ratio 48:25 (1.92). It is not 16:9, which is 1.778. The nearest named ratio is 1.91:1, about 0.52% off.

The last case is why the calculator reports the nearest named ratio with a percentage. A size can sit close to a named ratio without being on it, and the gap matters when a platform sets a tolerance.

Solving the missing side

Keep the ratio fixed and scale one side. With a known width W and a ratio A:B, the height is H = W × B ÷ A. With a known height, the width is W = H × A ÷ B.

A 16:9 frame 1280 pixels wide gives H = 1280 × 9 ÷ 16 = 720, a whole number. A 9:16 Story 1000 pixels wide gives H = 1000 × 16 ÷ 9 = 1777.78, which rounds to 1778. The rounded size is about 0.012% off an exact 9:16. Nobody will see that, but it explains why one tool says 1777 and another says 1778.

Solve with the exact numbers and round once, at the end. If you shorten 16:9 to 1.78 first, 1280 ÷ 1.78 = 719.1, which rounds to 719: one pixel short of the true 720.

To get a size with no rounding at all, reduce the ratio first. The width must then be a multiple of the first number, and the height a multiple of the second. Every pixel-exact 16:9 width is a multiple of 16: 1280 is 80 × 16, and 1920 is 120 × 16. Written in whole numbers, 1.91:1 is 191:100, so a pixel-exact width would have to be a multiple of 191. In practice nobody does that. Platforms that use 1.91:1 work with nearby sizes instead: LinkedIn recommends 1200 × 628, and Meta allows a 1% tolerance on Instagram feed image ads.

Common resolutions for each ratio

Only the 16:9 row comes from a platform. It is YouTube’s list of recommended 16:9 upload resolutions. The other rows are arithmetic (the ratio multiplied by a whole number), so they are labelled as calculated, not as anyone’s official spec.

The 16:9 row is YouTube’s list; every other row is calculated. Linked ratios and sizes open their own page.
RatioSizes (px)Basis
16:9YouTube's list. 854 × 480 and 426 × 240 are rounded, not exact 16:9.YouTube Help
16:1016:10 reduces to 8:5.Calculated
4:3Calculated
5:4Calculated
1:1
  • 1080 × 1080
  • 1200 × 1200
Calculated
4:5Calculated
3:4
  • 1080 × 1440
Calculated
9:16Calculated
3:2
  • 1500 × 1000
  • 3000 × 2000
Calculated
2:3
  • 1000 × 1500
Calculated
21:9
  • 2520 × 1080
Exactly 7:3. 2560 × 1080 and 3440 × 1440 are not 21:9.		Calculated
32:9Calculated

Two of YouTube’s own sizes are not exactly 16:9. 854 × 9 ÷ 16 = 480.375 and 426 × 9 ÷ 16 = 239.625, so 854 × 480 and 426 × 240 are rounded. A true 16:9 width is always a multiple of 16, and 854 and 426 are not.

21:9 is a marketing name, not a measurement. Two ultrawide monitor resolutions, 2560 × 1080 and 3440 × 1440, reduce to 64:27 (2.370) and 43:18 (2.389). Neither is 21:9 (2.333); an exact 21:9 frame at 1080 pixels tall is 2520 × 1080. The Wikipedia article on aspect ratios files the TVs marketed as “21:9 cinema displays” from 2009 to 2012 under 64:27.

32:9 is exactly two 16:9 frames side by side: 3840 × 1080 is two 1920 × 1080 frames, and 5120 × 1440 is two 2560 × 1440 frames.

Social and ad sizes, from the platforms’ own pages

We checked each size below on the platform’s help or ads-guide page on 2026-10-05. The Meta, YouTube and Facebook pages show no publication date, and LinkedIn’s shows only “Last updated: 2 months ago”, so our check date is the firmest date we can give. The “reduces to” figure is our arithmetic on their numbers.

Meta’s ads guide also publishes tolerances. Instagram feed image ads accept ratios from 400 × 500 (4:5) to 191 × 100 (1.91:1), within 1%. Facebook feed image ads list a 3% tolerance. That is why the crop table in the calculator marks sizes within 1% of a named ratio separately from exact matches.

The Facebook Page cover shows how a stated ratio and a file size can disagree. Facebook’s help page says the cover loads fastest as an 851 × 315 JPG, and that it displays at 16:9 on computers and 2.4:1 on phones. But 851 ÷ 315 = 2.70, and 851:315 does not reduce at all, so the file matches neither display shape. Expect part of it to be cropped on at least one screen, and keep anything important in the middle. The Facebook cover photo guide covers the layout.

Ordinary Instagram posts, as opposed to ads, are less clearly documented. Instagram’s own help page did not give us readable text. PetaPixel reported on 2025-05-29 that Instagram added 3:4 photos alongside 1:1 and 4:5, and that the maximum photo width stays at 1,080 pixels. The Instagram post size guide has the details. For banners, see the LinkedIn banner and Discord banner guides, or browse every size guide.

Which ratio should an ad use?

Meta’s ads guide recommends one ratio per placement:

  • Facebook feed and Instagram feed images: 4:5, 1440 × 1800.
  • Instagram Stories and Reels: 9:16, 1440 × 2560, with roughly the top 14%, bottom 35% and 6% on each side kept clear of text and logos.
  • Facebook feed carousel cards: 1:1, at least 1080 × 1080.
  • Landscape: 1.91:1 is the widest ratio the Instagram feed accepts for an image ad.

These recommendations are about how the image is displayed, not evidence that one ratio performs better. We have no performance data on that, and this page makes no such claim. If a single image ad will run in several placements, supplying an image at each placement’s ratio means the platform does not have to crop your subject to fit. Once the image fits, check the words that go with it in the Meta ad copy preview.

You do not need AdFlint, or any paid tool, to fix an image’s aspect ratio. This page and the free resizers in the size guides do it for nothing. A correctly sized creative also does not make an ad perform. The right ratio only prevents bad cropping; the platforms decide delivery.

Common mistakes

  1. Calling 1920 × 1000 “16:9” or 1080 × 566 “exactly 1.91:1” without checking the decimal. 1.92 is not 1.778, and 1.9081 is not 1.91.
  2. Rounding partway through, then rounding again, and ending up a pixel off.
  3. Swapping the terms. 16:9 is landscape; 9:16 is the same shape turned upright.
  4. Assuming a 3:4 phone photo already fits 4:5. Cropping 1080 × 1440 to 4:5 cuts 90 pixels of height, 6.25% of the image.
  5. Calling 2560 × 1080 “21:9”. It is 64:27, or 2.370.
  6. Putting text or a logo near the edges of a 9:16 Story or Reel image. Meta suggests keeping roughly the top 14%, the bottom 35% and 6% of each side clear.
  7. Stretching an image to fit a ratio. Crop it or add padding instead, so faces and text keep their shape.

Questions

How do you calculate aspect ratio?

Divide the width and the height by their greatest common divisor. For 1920 × 1080 the greatest common divisor is 120, so the ratio is 1920 ÷ 120 : 1080 ÷ 120 = 16:9. For a quick check, divide width by height: 1920 ÷ 1080 = 1.778, the same decimal as 16 ÷ 9.

What is 1920 × 1080 as an aspect ratio?

16:9, or 1.778:1. It is the 1080p entry in YouTube's list of recommended 16:9 upload resolutions.

How do I find the height for a 16:9 width?

Multiply the width by 9 and divide by 16. A 1280-pixel width gives 1280 × 9 ÷ 16 = 720. For any ratio A:B, height = width × B ÷ A, and width = height × A ÷ B.

What aspect ratio should an Instagram post or Story be?

For ads, Meta's ads guide recommends 4:5 at 1440 × 1800 for the Instagram feed and 9:16 at 1440 × 2560 for Stories and Reels (checked 2026-10-05). For regular posts, PetaPixel reported in May 2025 that Instagram added 3:4 photos alongside 1:1 and 4:5, and that the maximum photo width is still 1,080 pixels. We could not confirm the exact accepted range on Instagram's own help page.

What is the difference between 4:5 and 3:4?

4:5 is 0.8 units wide for every unit tall; 3:4 is 0.75, so it is slightly taller. A 1080 × 1440 phone photo (3:4) cropped to 4:5 becomes 1080 × 1350. That cuts 90 pixels of height, 6.25% of the image.

Why is 1.91:1 not exactly 1.91?

Because 1.91:1 is a rounded name. LinkedIn's recommended landscape ad image, 1200 × 628, reduces to 300:157, which is 1.9108. A 1080 × 566 image is 1.9081. Both get called 1.91:1. Meta's ads guide writes the widest Instagram feed ratio as 191 × 100.

Sources

All sources were last verified on 2026-10-05. Wikipedia is used only for the definition of aspect ratio and its note on “21:9” TVs.

What we could not confirm

  • Instagram’s help page for organic post sizes did not load readable text for us. The 3:4 change and the 1,080-pixel maximum width come from PetaPixel’s news report, not from Instagram.
  • The official pages cited here show no publication date, except LinkedIn’s relative “Last updated” note. “Last verified 2026-10-05” is the day we read them, not the day the platforms set the numbers.
  • We found no authoritative public list of 16:10, 5:4 or ultrawide monitor resolutions. The table’s rows for those ratios are exact multiples we calculated, not a list of what monitors ship with.
  • The image check uses the width and height your browser reports. We tested it only with an image that has no rotation tag, so a phone photo that has one may come out with width and height swapped in some browsers. If it does, use “Swap width and height”.

Look up a ratio or resolution

Vertical and social

Close to 16:9 or 1.91:1

Running paid ads on Google or Meta?

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