Aspect ratio calculator

1. Find a ratio. With the lock open, type a width and a height. The calculator shows the simplified ratio, the decimal, whether the shape is landscape or portrait, and the closest common ratio with where it is used.
2. Find a missing side. Pick a common ratio or type your own (you can type 16:9 straight into the first box). That locks the ratio. Now type a width to get the height, or a height to get the width.
3. Read a photo's size. Choose Read size from an image to fill in the width and height of a photo on your device. The file is opened in your browser, not uploaded.
4. Copy the result. Copy the ratio, the size or the decimal with one click, or pick one of the common sizes at your ratio.

The box beside the result is drawn to scale, and the formula box shows the maths with your own numbers. The ratio has no unit, so you can work in pixels, inches or centimeters, decimals included.

aspect ratio = (width ÷ GCD) : (height ÷ GCD)

GCD is the greatest common divisor, the largest whole number that divides both sides exactly.

Example: 1920 x 1080. The largest number that divides both is 120. 1920 ÷ 120 = 16 and 1080 ÷ 120 = 9, so the ratio is 16:9. Meta's own example works the same way: 1600 x 900 and 3200 x 1800 are both 16:9, and 1080 x 1350 is 4:5.

Finding a missing side

height = width × second number ÷ first number
width = height × first number ÷ second number

• 4:5 at 1080 pixels wide: 1080 × 5 ÷ 4 = 1350 pixels tall.
• 9:16 at 1000 pixels wide: 1000 × 16 ÷ 9 = 1777.78, so 1778 pixels tall once rounded to a whole pixel.
• 16:9 at 720 pixels tall: 720 × 16 ÷ 9 = 1280 pixels wide.

The decimal form

decimal = width ÷ height

1920 ÷ 1080 = 1.78, often written 1.78:1. Decimals make shapes easy to compare: anything above 1 is landscape, 1 is square, and below 1 is portrait. They also name shapes that do not simplify neatly. 1366 x 768 simplifies to 683:384, which is about 1.779, within 0.05% of 16:9.

Cropping a photo to a ratio

To get the largest crop of a given shape from a photo, keep the side that already fits and work out the other. A 4000 x 3000 camera photo (4:3) is wider than 4:5, so keep the full 3000 pixel height: width = 3000 × 4 ÷ 5 = 2400. The crop is 2400 x 3000, which you can then scale to 1080 x 1350. The Instagram image resizer does both steps for you.

Two shapes that are rounded names. 1.91:1 is not a whole-number ratio: 1200 x 628 simplifies to 300:157 and 1080 x 566 to 540:283, and both are about 1.91 to 1. "21:9" monitors are not exactly 21:9 either: 2560 x 1080 is 64:27 (2.37) and 3440 x 1440 is 43:18 (2.39).

Portrait and landscape are the same ratio turned. 9:16 and 16:9 are one shape on its side, as are 4:5 and 5:4. Writers usually put the width first, so 9:16 means taller than wide.

Meta recommends 4:5 for images in Facebook Feed and Instagram Feed, 9:16 for Stories and Reels, and 1:1 for Facebook carousel cards and Marketplace. Meta's advice for mobile is to cover as much of the screen as possible, and it notes that most people hold their phones upright.

How close does an image have to be? Meta allows a 3% aspect ratio tolerance for Facebook Feed and Facebook Reels, and 1% for Instagram placements and Facebook Stories. The calculator tells you how far a size is from the nearest common ratio, so you can see whether it falls inside those limits. When a size is off, crop or pad it to the exact shape with the Instagram image resizer or the Facebook image resizer.

For vertical ads, the shape is only half the job: Stories and Reels cover the top and bottom of the screen with buttons and captions. Check your layout with the Instagram Reels safe zone checker, and see every placement in our Meta ads specs guide.

Image Ads, part of CamClo AI, makes ad creatives from your product photos in the ratio you pick: 1:1, 4:5 and 9:16 for Instagram and Facebook, and 2:3, 1.9:1, 3:4, 3:2, 5:4 and 4:3 for other placements. Each creative is composed for its shape rather than cropped from another size, and for 9:16 it keeps important content away from the top and bottom of the frame, where Stories and Reels show their buttons.