Calculating Aspect Ratio — Free Aspect Ratio Calculator
Calculate aspect ratios for images, videos, and screens. Enter width and height to find the ratio, or lock a ratio and calculate missing dimensions. Common presets for 16:9, 4:3, 1:1, and more. Free and private.
Common Aspect Ratios
How Aspect Ratio Calculator Works
Calculating aspect ratio means reducing width and height to their simplest whole-number pair. Find the greatest common divisor (GCD) of the two numbers and divide both by it: 1920 × 1080 has a GCD of 120, so it becomes 16:9. Enter any width and height above and this calculator does it instantly in your browser.
What Is Aspect Ratio?
Aspect ratio is the proportional relationship between the width and height of an image, video, or screen. It is expressed as two numbers separated by a colon, like 16:9 or 4:3. The aspect ratio calculator helps you maintain correct proportions when resizing images, designing layouts, or choosing display resolutions.
Common Aspect Ratios
16:9 — HD video, YouTube, most monitors
4:3 — Classic TV, iPad, presentations
1:1 — Instagram square, profile pictures
9:16 — TikTok, Instagram Reels, Stories
21:9 — Ultrawide monitors, cinematic
Aspect Ratio for Video
Most modern video content uses 16:9 (widescreen). YouTube, Netflix, and most streaming platforms default to this ratio. Vertical video for TikTok and Instagram Reels uses 9:16. Cinematic films often use wider ratios like 21:9 or 2.39:1. When editing video, maintaining the correct aspect ratio prevents black bars or stretching.
Aspect Ratio for Web Design
Web designers use aspect ratios to create responsive image containers, hero sections, and video embeds. CSS provides the aspect-ratio property to maintain proportions without JavaScript. Common web image ratios include 16:9 for hero banners, 1:1 for thumbnails, and 4:3 for product photos.
How to Determine Aspect Ratio: Worked Example and Quick Reference
Take a 1600 x 900 screen. The largest number that divides both values is 100, so 1600 ÷ 100 = 16 and 900 ÷ 100 = 9. The 1600 x 900 aspect ratio is therefore 16:9, the same shape as 1920 × 1080. The decimal check gives the same answer: 1600 ÷ 900 = 1.778, and every 16:9 size shares that value.
Use the table below to match a resolution to its ratio, or pick a preset above and type one side to get the other.
| Ratio | Width ÷ height | Example resolutions |
|---|---|---|
| 16:9 | 1.778 | 1280 × 720, 1600 × 900, 1920 × 1080, 3840 × 2160 |
| 4:3 | 1.333 | 800 × 600, 1024 × 768, 1600 × 1200 |
| 3:4 | 0.75 | 768 × 1024, 1080 × 1440 |
| 3:2 | 1.5 | 1080 × 720, 1440 × 960, 6000 × 4000 |
| 1:1 | 1 | 1080 × 1080 |
A 3:4 aspect ratio is simply 4:3 turned on its side, so swap width and height to move between them.
Tips for Getting Accurate Results
For the most accurate results, use up-to-date numbers from official sources. Double-check your inputs before calculating — small errors in the starting values can lead to significantly different outputs. If you are comparing scenarios, keep all variables the same except the one you are testing. Save or screenshot your results for future reference. This calculator uses standard formulas and is designed to give you a reliable quick estimate, though professional advice may be needed for complex situations.
Frequently Asked Questions
What is 16:9 aspect ratio in pixels?
Common 16:9 resolutions include 1920×1080 (Full HD), 2560×1440 (2K), 3840×2160 (4K), and 1280×720 (HD). Any resolution where width÷height = 1.778 is 16:9.
What aspect ratio is Instagram?
Instagram supports 1:1 (square), 4:5 (portrait), and 1.91:1 (landscape). Stories and Reels use 9:16 (vertical). The recommended resolution for feed posts is 1080×1080 (square) or 1080×1350 (portrait).
How do I calculate aspect ratio?
Divide both width and height by their Greatest Common Divisor (GCD). For example, 1920÷120=16 and 1080÷120=9, giving 16:9.
What aspect ratio is 1600 x 900?
1600 x 900 is a 16:9 aspect ratio. The greatest common divisor of 1600 and 900 is 100, and 1600÷100=16, 900÷100=9. Its decimal value, 1.778, matches every other 16:9 size such as 1920×1080.
What are common 4:3 aspect ratio resolutions?
Common 4:3 resolutions include 800×600, 1024×768 and 1600×1200 — each one divides to 1.333. Turn them on their side (for example 768×1024) and you get the 3:4 portrait ratio.
What is the best aspect ratio for YouTube?
YouTube uses 16:9 as its standard player ratio. Upload videos at 1920×1080 (Full HD) or 3840×2160 (4K) for best quality. YouTube Shorts use 9:16 vertical format.
Is Aspect Ratio Calculator free to use?
Yes, Aspect Ratio Calculator is completely free with no sign-up, no login, and no hidden fees. The tool runs entirely in your browser — your data never leaves your device.