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.