Calculators
Aspect Ratio Calculator
Find the simplified aspect ratio of any width and height, and the matching height for a new width.
About the Aspect Ratio Calculator
The Aspect Ratio Calculator finds the simplified ratio of any width and height, shows the shape as a preview box, and works out the matching height for a new width, or the width for a new height. Tap common ratios like 16:9, 4:3, 1:1 or 9:16, and pick standard resolutions for each.
What you can do with the Aspect Ratio Calculator
- Simplify any ratio: 1920 × 1080 becomes 16:9.
- Shape preview: A box shows the shape.
- Resize helper: Find the matching height for a new width, or the other way round.
- Common ratios: 16:9, 4:3, 1:1, 9:16 with standard resolutions.
Common ratios
16:9 is the standard for TVs, laptops and YouTube. 9:16 is the same shape on its side, used for Stories, Reels and Shorts. 4:3 is older screens and many tablets, 3:2 is most cameras, 1:1 is square posts, 4:5 is Instagram portrait, and 21:9 is ultrawide monitors.
Resizing without stretching
To make an image or video smaller or bigger without distortion, keep the ratio the same. Enter a new width and the calculator gives the matching height, or the other way round.
When the ratio looks strange
Some screen sizes, like 1366 × 768, don't simplify neatly, that one is exactly 683:384, which is very close to 16:9. The calculator shows both the nearest common ratio and the exact one.
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Frequently Asked Questions
What aspect ratio is 1920 × 1080?
16:9.
How do I calculate the height for a new width?
Height = new width × original height ÷ original width. Type the new width in "Resize and keep the shape".
What size should a YouTube thumbnail be?
1280 × 720 pixels, which is 16:9.
What sizes should I use for Instagram posts and Reels?
Common sizes are 1080 × 1080 for a square 1:1 post, 1080 × 1350 for a 4:5 portrait post, and 1080 × 1920 for 9:16 Reels and Stories. Tap the 1:1, 4:5 or 9:16 chip to see these standard sizes.
What aspect ratio is a 1080 × 2400 phone screen?
1080 × 2400 simplifies to 9:20, because both numbers divide by 120. Many modern phones use tall ratios like this, so 9:16 videos may show small black bars or be cropped slightly when shown full screen.
What aspect ratio is A4 paper?
A4 is 210 × 297 mm. Enter those numbers and the calculator shows 70:99, which is about 0.7071 : 1 in portrait. All A-series paper sizes use a ratio of 1 to the square root of 2, about 1:1.414.
What does MP mean in the result?
MP stands for megapixels: width × height ÷ 1,000,000. A 4000 × 3000 photo is 12 MP and has a 4:3 ratio. A 1920 × 1080 image is about 2.07 MP.
How do I fit a 4:3 photo into a 16:9 frame?
You either crop or add bars. Keeping the full width of a 4000 × 3000 photo, a 16:9 crop is 4000 × 2250, so 750 pixels of height are cut. Adding bars at the sides instead keeps the whole picture.
Will resizing an image stretch it?
Only if the new width and height have a different ratio from the original. Use the "Resize and keep the shape" card: enter a new width or height and it gives the matching other side, so the picture keeps its proportions.
Can I enter a new height instead of a new width?
Yes. Type in the New height box and the width is worked out for you; the other box clears so only one side drives the result. The result is rounded to whole pixels, with the exact value shown below.
What does the decimal ratio such as 1.7778 : 1 mean?
It is the width divided by the height. 16:9 is 1.7778 : 1, 4:3 is 1.3333 : 1 and 21:9 is about 2.33 : 1. It helps compare ratios that do not simplify neatly, and shows whether a shape is landscape, portrait or square.
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