Aspect Ratio Calculator
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About Aspect Ratios
Every screen, photo, print, and video frame has an aspect ratio, and mismatches are why exports get black bars, uploads get cropped mid-face, and client logos arrive stretched. The ratio — not the resolution — decides whether content fits: 1920×1080 and 1280×720 are different sizes but the same 16:9 shape.
Enter your original dimensions to get the simplified ratio and its common name, plus a proportional scale to any new width. Designers use it for responsive images, video editors for export presets, photographers for print sizes, and social posters for the eternal 1:1 / 9:16 / 16:9 triangle.
Ratios are fractions wearing a colon — simplify and compare them with the Fraction Calculator
The Ratio & Scaling Math
Two operations cover everything:
Ratio = (W ÷ GCD) : (H ÷ GCD) New height = new width × H ÷ W
Worked example: 1920 × 1080 → GCD 120 → 16:9; scaling to 1280 wide gives 1280 × 1080 ÷ 1920 = 720. Watch the ultrawide gotcha: “21:9” marketing screens are actually 64:27 (2560×1080) — close to, but not exactly, 21:9 = 2.333.
Common Ratios & Resolutions
The formats you'll actually meet, with their standard resolutions:
| Ratio | Used for | Common resolutions |
|---|---|---|
| 16:9 | Video, TV, YouTube, monitors | 1280×720, 1920×1080, 3840×2160 |
| 9:16 | Vertical video — Reels, TikTok, Stories | 1080×1920 |
| 4:3 | Classic TV, iPad, older photos | 1024×768, 2048×1536 |
| 3:2 | 35mm photos, many laptops | 3000×2000, 2160×1440 |
| 16:10 | MacBook & productivity laptops | 1920×1200, 2560×1600 |
| 1:1 | Instagram grid, avatars | 1080×1080 |
| 64:27 (~21:9) | Ultrawide monitors, cinema | 2560×1080, 3440×1440 |
| 2:3 / 5:4 | Portrait prints (4×6, 8×10) | 1200×1800, 1600×2000 |
Print reminder: an 8×10 print is 5:4, but a 35mm photo is 3:2 — that's why 8×10s crop your photos and 4×6s don't.
Cropping vs Letterboxing
When source and destination ratios differ, something has to give: cropping cuts content to fill the frame (Instagram's default), letterboxing/pillarboxing adds bars to preserve everything (YouTube showing vertical video), and stretching distorts — the one option that's always wrong. Pick per use: crop for impact when edges are expendable, letterbox when every pixel matters.
The professional workflow avoids the choice: shoot or design at the destination ratio from the start, and when one asset feeds many formats (a 16:9 hero that must also be a 1:1 thumbnail and a 9:16 story), compose with a central “safe zone” that survives every crop. This calculator tells you exactly what each target's dimensions are.
Frequently Asked Questions
How do I calculate an aspect ratio?
Divide both dimensions by their greatest common divisor: 1920 and 1080 share a GCD of 120, giving 16:9. Odd dimensions may not reduce nicely — 1366×768 is technically 683:384, which is why it's just called “roughly 16:9.”
What is the aspect ratio of 1920×1080?
16:9 — the standard for HD video, YouTube, TVs, and most monitors. 1280×720 and 3840×2160 (4K UHD) are the same shape at different sizes, so content moves between them without cropping.
How do I resize without stretching?
Scale both dimensions by the same factor: new height = new width × original height ÷ original width. Taking 1920×1080 to 1280 wide means 720 tall — any other height distorts or requires cropping.
What aspect ratio for Instagram, TikTok, and YouTube?
YouTube: 16:9 (1920×1080). TikTok/Reels/Stories: 9:16 vertical (1080×1920). Instagram grid: displays 1:1 (feed posts also accept 4:5 portrait). One shoot feeding all three is exactly the safe-zone problem — keep the subject centered.
Is 21:9 really 21:9?
Marketing rounds it: 2560×1080 reduces to 64:27 (≈2.37:1), slightly wider than a true 21:9 (2.33:1). It's cinema's ~2.39:1 heritage adapted to monitors — close enough for buying decisions, worth knowing for pixel-exact design.
What's the difference between aspect ratio and resolution?
Resolution is the pixel count (1920×1080); aspect ratio is the shape (16:9). Same ratio at different resolutions scales cleanly; same resolution count in a different shape (1920×1200 is 16:10) doesn't. Fit is decided by ratio, sharpness by resolution.
Methodology. This calculator uses standard, peer-reviewed mathematical formulas. It is reviewed and maintained by the Vast Calculators editorial team.
Last updated · July 2026
Results are estimates for general use; verify critical figures independently.