Aspect Ratio Calculator

Find the ratio of any size, or calculate a missing width/height while keeping proportions.

Ratio: 16:9 · 1920 × 1080

Edit the pixel width and the height updates to match the ratio (and vice versa). Edit the ratio fields to change the locked proportions.

Common aspect ratios cheat sheet

  • 16:9 — YouTube, TV, monitors, presentations. 1920×1080, 3840×2160 (4K).
  • 9:16 — TikTok, Reels, YouTube Shorts, phone wallpapers. 1080×1920.
  • 1:1 — Instagram feed, profile pictures. 1080×1080.
  • 4:5 — Instagram portrait posts. 1080×1350.
  • 4:3 — older monitors, iPad screens, classic photography. 1024×768, 2048×1536.
  • 21:9 — ultrawide monitors and cinematic video. 2560×1080, 3440×1440.
  • 3:2 — DSLR photos, many laptop screens. 3000×2000.

How the math works

An aspect ratio is just a fraction. If your ratio is 16:9 and you know the width W, the height is W × 9 ÷ 16. Going the other way, height H gives a width of H × 16 ÷ 9. To find the ratio of an existing image, divide both dimensions by their greatest common divisor — 1920×1080 reduces to 16:9. This calculator handles the rounding for you and warns you implicitly: if a result is not a whole pixel, it rounds to the nearest one.

Frequently Asked Questions

How do I calculate aspect ratio from width and height?

Divide both numbers by their greatest common divisor. For example, 1920 and 1080 share a divisor of 120, giving 16:9. This calculator does it instantly — enter any width and height and the simplified ratio appears.

What resolution is 16:9?

Common 16:9 resolutions include 1280×720 (HD), 1920×1080 (Full HD), 2560×1440 (QHD), and 3840×2160 (4K UHD). Enter your target width in the calculator with the 16:9 preset selected to get the matching height.

How do I resize an image without stretching it?

Keep the ratio locked: enter the original width and height, then type your new width — the calculator gives you the exact height that preserves the proportions, so nothing looks squashed or stretched.

What aspect ratio should I use for YouTube, Instagram, and TikTok?

YouTube videos are 16:9 (1920×1080). YouTube Shorts, TikTok and Instagram Reels are 9:16 (1080×1920). Instagram feed posts work best at 1:1 (1080×1080) or 4:5 (1080×1350).

What is the difference between aspect ratio and resolution?

Resolution is the actual pixel count (1920×1080); aspect ratio is only the shape — the proportional relationship between width and height (16:9). Many different resolutions can share the same aspect ratio.