Aspect Ratio Calculator

Calculate missing width or height from any aspect ratio. Get platform-specific dimensions for YouTube, Instagram, TikTok, Twitter, Facebook and more. Includes ratio presets, resize calculator, and visual preview.

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Common Ratios
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Common Aspect Ratios Explained

An aspect ratio is the proportional relationship between the width and height of an image or video. It is written as W:H — for example 16:9 means for every 16 units of width there are 9 units of height.

Ratio Common Use Example Size
16:9 YouTube, TV, most videos 1920×1080, 1280×720
9:16 TikTok, Instagram Reels, Stories 1080×1920
1:1 Instagram posts, profile pictures 1080×1080
4:5 Instagram portrait posts 1080×1350
4:3 Old TV, presentations 1024×768, 800×600
21:9 Ultrawide monitors, cinematic 2560×1080
3:2 DSLR photos, 35mm film 3000×2000
2:1 Twitter header, panoramas 1500×750

Platform-Specific Dimensions

Platform & Use Size Ratio
YouTube Thumbnail 1280×720 16:9
YouTube Banner 2560×1440 16:9
Instagram Post (Square) 1080×1080 1:1
Instagram Post (Portrait) 1080×1350 4:5
Instagram Story / Reel 1080×1920 9:16
TikTok Video 1080×1920 9:16
Twitter Post Image 1200×675 16:9
Twitter Header 1500×500 3:1
Facebook Cover 820×312 ~2.6:1
LinkedIn Cover 1584×396 4:1
OG Image (SEO) 1200×630 ~1.9:1

Common Aspect Ratios and When to Use Them

Aspect ratio describes the proportional relationship between an image or video's width and height, and choosing the wrong one for a platform often results in awkward cropping or letterboxing. This calculator scales any given width or height to match a target ratio, or lets you compute the ratio of an existing pair of dimensions.

Different platforms and formats favor different standard ratios: 16:9 is the standard for widescreen video (YouTube, most TVs), 4:3 was the older standard television and early digital photo ratio, 1:1 (square) suits Instagram feed posts and profile images, and 9:16 (vertical) is the standard for Instagram Reels, TikTok, and YouTube Shorts.

  • 16:9 (Widescreen): Standard for YouTube videos, most modern TVs and monitors.
  • 4:3 (Standard): Older TV and photo standard, still used for some presentation formats.
  • 1:1 (Square): Common for Instagram feed posts and profile pictures.
  • 9:16 (Vertical): Standard for Reels, TikTok, YouTube Shorts, and Stories.

Frequently Asked Questions

Everything about aspect ratios and image dimensions

16:9 is the standard aspect ratio for YouTube. The recommended resolution is 1920×1080 (Full HD) or 3840×2160 (4K). YouTube thumbnails should also be 16:9 at 1280×720 pixels minimum. Videos shot in 9:16 (vertical) will have black bars on YouTube's horizontal player.
Instagram supports multiple ratios. For feed posts: 1:1 (square, 1080×1080) or 4:5 (portrait, 1080×1350) get the most screen real estate. For Stories and Reels: 9:16 (1080×1920). Portrait posts (4:5) tend to perform best as they take up the most space in the feed.
Divide both width and height by their Greatest Common Divisor (GCD). For example 1920×1080: GCD = 120, so 1920/120 = 16 and 1080/120 = 9. Ratio = 16:9. Use the "Find Ratio" mode in the calculator above to do this automatically.
16:9 is a wide (widescreen) format used in modern TVs, monitors, and most online video. 4:3 is a squarish format used in older TVs and monitors, still common in presentations. On a 16:9 screen, 4:3 content will have black bars on the sides (pillarboxing).
Multiply both dimensions by the same scale factor. For example to resize 1920×1080 to half size: 1920×0.5 = 960, 1080×0.5 = 540. Use the "Resize" mode in this calculator to do this automatically while keeping the ratio locked.
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