Aspect Ratio Calculator
Aspect Ratio — What It Is and Why It Matters
Aspect ratio is the relationship between a image or video's width and height, expressed as two numbers separated by a colon. It determines how content looks on different screens and platforms — and using the wrong ratio is one of the most common causes of letterboxing, cropping, and distorted content.
How to Use This Calculator
In Find ratio mode: enter any width and height to get the simplified aspect ratio and decimal equivalent. In Scale mode: select a standard ratio, enter one known dimension, and find the other — useful for resizing images and videos while maintaining proportions.
How Ratios Are Simplified
GCD is the Greatest Common Divisor of width and height. For 1920×1080: GCD = 120 → 1920÷120 = 16, 1080÷120 = 9 → 16:9. For 1280×960: GCD = 320 → 4:3. Some ratios like 2.35:1 (cinemascope) cannot simplify to whole numbers.
Common Aspect Ratios by Platform
- 16:9 — YouTube, widescreen TVs, monitors, presentations. The dominant ratio for all HD and 4K content.
- 4:3 — Older TVs, some webcams, legacy presentations. Rarely used for new content.
- 1:1 (square) — Instagram feed posts, Facebook posts. Equal dimensions in both orientations.
- 9:16 (vertical) — TikTok, Instagram Reels, YouTube Shorts, Stories. The mobile-first portrait format.
- 4:5 — Instagram portrait posts. Taller than square, takes up more feed space.
- 3:2 — DSLR photography (35mm film origin). Most mirrorless cameras shoot in this ratio natively.
- 21:9 (ultrawide) — Cinematic productions, ultrawide monitors. Creates the "widescreen movie" look.
- 2.35:1 (cinemascope) — Classic cinema format. The wide black bars above and below video in theatrical films.
Frequently Asked Questions
What happens if I upload a video in the wrong aspect ratio?
Most platforms either letterbox (add black bars), pillarbox (add black side bars), or crop the content to fit their native display ratio. YouTube auto-adds black bars for non-16:9 content. Instagram may crop your image at upload. Always export at the native ratio of your target platform for the best result.
How do I scale an image to a specific aspect ratio without distorting it?
Use the Scale mode in this calculator — enter your target ratio and one known dimension, and it calculates the other dimension while maintaining the exact ratio. This ensures no stretching or squashing.
What's the difference between 16:9 and 16:10?
16:10 is slightly taller than 16:9 and was the dominant monitor ratio before widescreen TV standards took over. Many older laptops use 16:10. In practice, 16:10 content on a 16:9 display has very thin horizontal letterbox bars, and vice versa — the difference is small but visible.
What aspect ratio should I use for print?
Print has different standards than digital. Standard photo prints are 4×6 (2:3 ratio), 5×7, and 8×10 — none of which match the 16:9 or 4:3 ratios of most cameras and monitors, which is why photos get cropped when printing. Frame your composition to the intended print size's ratio when shooting. For business cards and documents, the ISO A standard (~1:1.414) is used across most of the world.
Why do some videos have black bars on the sides instead of top and bottom?
Vertical black bars (pillarboxing) appear when 4:3 or 9:16 content plays on a 16:9 widescreen display — the content is narrower than the screen. Horizontal black bars (letterboxing) appear when 21:9 or 2.35:1 ultrawide content plays on a 16:9 display. Platforms like YouTube show pillar bars for vertical videos on desktop. Always export at the exact pixel dimensions of your target platform to avoid any bars.