Aspect Ratio Calculator
An aspect ratio is the shape of a screen, image or video: its width compared with its height. Find the ratio of any size, or resize to a ratio without stretching. As a 16:9 or resolution calculator, enter a width and it gives the matching height.
How do you calculate an aspect ratio?
Divide the width and the height by the largest number that goes into both. For 1920 × 1080 that number is 120, which leaves 16 and 9, so the ratio is 16:9.
For a decimal ratio, divide the width by the height instead. 1920 ÷ 1080 is 1.78, written 1.78:1.
What are the common aspect ratios?
Why is a 21:9 monitor not exactly 21:9?
21:9 is a marketing name. A 3440 × 1440 ultrawide works out to 43:18, or 2.39:1, and 2560 × 1080 to 64:27, or 2.37:1. Both are close to 21:9, which is 2.33:1.
How do I resize without stretching?
Keep the ratio the same. New height = new width × ratio height ÷ ratio width, so a 16:9 image 1280 pixels wide must be 720 pixels tall.
If the new shape differs, crop the picture or add bars at the sides or the top and bottom instead.
How do I find the aspect ratio of an image?
First find its size in pixels, then enter the width and height in the calculator above. Your computer shows the size in a few clicks:
- Windows: right-click the file, choose Properties, then the Details tab. Width and height are listed under Image.
- Mac: open the image in Preview and choose Tools, then Show Inspector. The size is shown in pixels.
- iPhone: open the photo in Photos and swipe up. The details show the size in pixels.
The same works for a video frame or any picture. A photo of 4032 × 3024 pixels, common on phones, is 4:3.
What are the 16:9 resolutions?
Every one of these is exactly 16:9, so each scales to the next without bars or cropping:
- 1280 × 720 (HD, 720p)
- 1600 × 900 (HD+)
- 1920 × 1080 (Full HD, 1080p)
- 2560 × 1440 (QHD, 1440p)
- 3840 × 2160 (4K UHD)
- 7680 × 4320 (8K UHD)
For any other width, multiply by 9 and divide by 16 to get the height. For a height, multiply by 16 and divide by 9. A 1000 pixel wide 16:9 frame is 562.5 pixels tall, so round to 562 or 563, or pick a width that divides by 16.
How do I change a photo to another aspect ratio?
You can crop it or add borders. Cropping cuts the long side down to the new shape and keeps the picture full. Borders keep the whole picture but add bands of color around it.
Most photo apps crop to a set ratio. On an iPhone, open the photo, tap Edit, then the crop tool, and choose a ratio such as square or 16:9. Use the calculator first to see how many pixels each crop keeps.
What aspect ratio should I use for video?
Use 16:9 for YouTube and most other video, at 1920 × 1080 or 3840 × 2160. Use 9:16, the same shape stood upright, for Shorts, Reels and TikTok. Instagram feed posts suit 4:5 or 1:1.
What aspect ratio are photos?
Most phone cameras shoot 4:3, while many larger cameras shoot 3:2. Prints have shapes of their own, so check the ratio before you order. A 4:3 photo needs a little cropping for a 6 × 4 in (15 × 10 cm) print, which is 3:2.
Questions
Does the unit matter?
No. A ratio has no unit, so pixels, inches or centimeters all give the same answer. Just use the same unit for width and height.
Is 1366 × 768 a 16:9 resolution?
Almost. It works out to 683:384, which is 1.78:1, so it is sold and shown as 16:9.
How do I keep the ratio when I resize an image?
Change one side and let the other follow. Enter the ratio and the new width above, and the height you need appears straight away.
How we measure
The exact ratio divides width and height by their greatest common divisor. The common name is shown when the ratio is within 1% of a standard one, such as 16:9.