Aspect Ratio Calculator
Find an aspect ratio, calculate a missing dimension, or scale any size while keeping the ratio.
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Common Aspect Ratios
| Ratio | Example Sizes | Typical Use |
|---|---|---|
| 16:9 | 1920×1080, 1280×720, 3840×2160 | HD/4K video, YouTube, TV, monitors |
| 4:3 | 1024×768, 800×600, 1400×1050 | Traditional TV, older monitors, iPad |
| 1:1 | 1080×1080, 500×500 | Instagram square, avatars, profile photos |
| 9:16 | 1080×1920, 720×1280 | Mobile video, TikTok, Instagram Stories, Reels |
| 21:9 | 2560×1080, 3440×1440 | Ultrawide monitors, cinematic films |
| 3:2 | 3000×2000, 6000×4000 | DSLR cameras, most photography |
| 2:3 | 2000×3000, 4×6 prints | Portrait photography prints |
| 4:5 | 1080×1350 | Instagram portrait (optimal reach) |
What Is Aspect Ratio?
Aspect ratio is the proportional relationship between an image's width and height, expressed as W:H where the numbers are reduced to their smallest whole numbers using the greatest common divisor (GCD). A 1920×1080 image has a GCD of 120, so 1920÷120 = 16 and 1080÷120 = 9, giving us 16:9.
How to Scale Without Distortion
To scale an image while preserving the ratio: New Height = New Width × (Original Height ÷ Original Width). For a 1920×1080 image scaled to 1280 wide: 1280 × (1080 ÷ 1920) = 1280 × 0.5625 = 720 pixels.
Frequently Asked Questions
YouTube's recommended ratio is 16:9 at 1920×1080 (1080p) or 3840×2160 (4K). Other ratios are accepted but letterboxed or pillarboxed.
For feed posts: 1:1 (square) or 4:5 (portrait, which gets more space on mobile). For Stories and Reels: 9:16 (vertical). For landscape: 1.91:1.
4K typically means 3840×2160 pixels (UHD), which is a 16:9 ratio. Cinema 4K (DCI 4K) is 4096×2160 — a slightly wider 19:10 ratio. Both are called "4K."
Use the Euclidean algorithm: divide the larger number by the smaller, take the remainder, repeat until the remainder is 0. The last non-zero remainder is the GCD. For 1920 and 1080: 1920 = 1×1080 + 840 → 1080 = 1×840 + 240 → 840 = 3×240 + 120 → 240 = 2×120 + 0. GCD = 120.
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