Free Aspect Ratio Calculator: Find Width, Height, or Ratio With Visual Preview
Enter any two of width, height, or aspect ratio — we compute the third and show a to-scale visual rectangle. Eleven preset ratios covering YouTube, TikTok, Instagram, cinema, photography, and Open Graph. Auto-reduces to lowest integer terms.
Click any lock icon to fix that field. Edits to the other two will recompute around it.
Simplified ratio
16:9
Decimal ratio
1.7778
width ÷ height
Dimensions
1920 × 1080
Orientation
Landscape
1.78× wider
Common ratios
Three-Way Calculation
Lock any one of {ratio, width, height} and we compute the other two. Edit any field to switch the lock — no separate modes or tabs.
Eleven Built-In Presets
YouTube 16:9, TikTok 9:16, Instagram 1:1 and 4:5, Open Graph 1.91:1, Cinemascope 2.35:1, photography 3:2, ultrawide 21:9, and more.
Lowest-Terms Reduction
GCD-based reduction simplifies any width/height pair to lowest integer terms — 1920×1080 becomes 16:9, 4032×3024 becomes 4:3.
100% Client-Side
No data leaves your browser — no signup, no tracking. The math runs instantly via JavaScript and works offline once loaded.
Lock Any Dimension, Compute the Rest — Without the Mental Math
Aspect ratio math is one of those everyday tasks that looks trivial until you have to do it during a deadline. What height for a 1500 px wide hero image at 16:9? What width for a 9:16 Stories asset 1080 tall? Is 3024×4032 the same ratio as 3:2 or 4:3? Our Free Aspect Ratio Calculator takes any two of {ratio, width, height} and computes the third in real time. Lock the dimension you want fixed, change the others, and the locked field stays put. The visual scaled-rectangle preview keeps proportions honest at a glance.
Pair this with our Favicon Generator (square 1:1 ratio for every browser/iOS/PWA size), CSS Filter Generator (apply visual treatment to assets at any ratio), Color Picker (sample brand colors from reference images), and the Meta Tag Previewer (verify your 1.91:1 og:image renders correctly across Facebook, X, LinkedIn).
Aspect Ratios by Platform (2026)
| Platform | Required Ratio | Recommended Dimensions |
|---|---|---|
| YouTube video | 16:9 | 1920×1080 (HD), 3840×2160 (4K) |
| YouTube thumbnail | 16:9 | 1280×720 minimum |
| YouTube Shorts | 9:16 | 1080×1920 |
| Instagram feed (square) | 1:1 | 1080×1080 |
| Instagram feed (portrait) | 4:5 | 1080×1350 |
| Instagram Stories / Reels | 9:16 | 1080×1920 |
| TikTok video | 9:16 | 1080×1920 |
| X / Twitter post image | 16:9 | 1200×675 |
| LinkedIn cover | 4:1 | 1584×396 (personal); 1128×191 (company) |
| Facebook cover | 2.7:1 | 820×312 (desktop) |
| Open Graph image | 1.91:1 | 1200×630 |
| Pinterest pin | 2:3 | 1000×1500 |
| Cinema (Cinemascope) | 2.39:1 | Theatrical wide release |
Each platform may update its specs periodically. Always check the platform's current developer docs before mass-producing assets.
The Aspect Ratio Math, Worked Out
1. Width → Height (locked ratio)
height = width × (ratio_h ÷ ratio_w)
Example: width 1500, ratio 16:9 → height = 1500 × (9 ÷ 16) = 843.75 px
2. Height → Width (locked ratio)
width = height × (ratio_w ÷ ratio_h)
Example: height 720, ratio 16:9 → width = 720 × (16 ÷ 9) = 1280 px
3. W & H → Ratio (lowest terms)
ratio = (w ÷ GCD(w,h)) : (h ÷ GCD(w,h))
Example: 1920×1080 → GCD = 120 → 1920÷120 : 1080÷120 = 16:9
4. Decimal Ratio
decimal = width ÷ height
16:9 → 1.7778 · 4:3 → 1.3333 · 1:1 → 1.0 · 9:16 → 0.5625
Common Aspect Ratio Mistakes
1. Swapping W and H
9:16 is portrait, 16:9 is landscape. Get them backwards and your TikTok video shows up sideways on YouTube and vice versa.
2. Ignoring Safe Zones
A 9:16 Stories video that puts critical content (text, faces) in the top or bottom 15% will be obscured by the platform UI overlay. Center critical content vertically.
3. Subpixel Heights
Math may produce 843.75 px; image software needs integers. Round UP (ceil) to avoid leaving an extra pixel-row uncovered by the asset.
4. Letterbox vs Crop Confusion
Letterboxing adds bars to preserve content; cropping removes content to fit. Different platforms default to different behaviors — produce assets at the platform-native ratio when possible.