Enter a width and height, such as 1920 × 1080, and the calculator simplifies it to its aspect ratio (16:9), shows the ratio as a decimal and names the closest standard format. Type a new width or a new height and the other side is calculated so the picture keeps exactly the same shape.
Use it to resize photos without stretching them, pick video export sizes for YouTube, Instagram Reels or TikTok, size a banner or a screen layout, or check whether a monitor resolution is 16:9 or 16:10. A preview box shows the shape, and presets set the most common ratios in one click.
How to use the Aspect Ratio Calculator tool
- Enter the original width and height, or click a preset such as 16:9.
- Read the simplified aspect ratio and the closest common ratio.
- Type a new width (or height) in the New size boxes.
- The missing side is filled in automatically, rounded to whole pixels if you like.
Why use ToolOrca Aspect Ratio Calculator
- Simplifies any size to its ratio
- Resize by width or by height
- Presets for 16:9, 4:3, 1:1, 9:16, 21:9 and more
- Closest standard ratio
- Live shape preview
- Works with decimals
How to calculate an aspect ratio
Divide the width and 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. To resize while keeping the ratio, use new height = new width × height ÷ width; for a 1280-pixel-wide 16:9 image that gives 1280 × 9 ÷ 16 = 720.
Common aspect ratios and sizes
16:9 is the standard for HD video, YouTube and most TVs and laptops (1280×720, 1920×1080, 3840×2160). 9:16 is vertical video for TikTok, Reels and Shorts (1080×1920). 4:3 is classic TV, iPad screens and many compact cameras. 3:2 is the shape of 35 mm film and most DSLR photos. 1:1 is a square post, and 4:5 is the tallest portrait Instagram allows in the feed. 21:9 is ultrawide monitors and cinema.
Frequently asked questions
What is the aspect ratio of 1920×1080?
1920×1080 is 16:9. So are 1280×720, 2560×1440 and 3840×2160 (4K UHD).
What size is 9:16 for TikTok and Reels?
The recommended size is 1080 × 1920 pixels. Any size with the same ratio, such as 720 × 1280, also fits.
Is 1366×768 exactly 16:9?
Almost. 1366 × 768 simplifies to 683:384, which is 1.7786:1, very close to 16:9 (1.7778:1). The calculator shows 16:9 as the closest common ratio.
How do I resize an image without stretching it?
Keep the aspect ratio: enter the original size here, type the new width and use the height it calculates. Then use our image resizer with those numbers.
What is the difference between 16:9 and 16:10?
16:10 (1.6:1) is slightly taller than 16:9 (1.78:1). Many laptops such as MacBooks use 16:10, for example 1920×1200 or 2560×1600.