Aspect Ratio Calculator
Calculate missing dimensions, detect image ratios, and find contain or cover fit dimensions for any box.
Ratio Presets
Calculate Missing Dimension
→ Height: 1080 px
→ Width: 1920 px
Using ratio 16:9
Image Fit Calculator
Ratio: 16:9
About this tool
A three-in-one aspect ratio tool: calculate the missing dimension from a known width or height, detect the aspect ratio of any image, and compute how an image fits inside a target box using contain (letterbox) or cover (crop) scaling. Includes presets for common ratios: 16:9, 4:3, 1:1, 9:16, 21:9, and more.
How to use it
Quick steps to get the most out of this utility.
- 1
Pick a preset or enter a custom ratio
Choose 16:9, 4:3, 1:1, etc., or type any custom W:H ratio.
- 2
Calculate a missing dimension
Enter width to get height, or height to get width.
- 3
Use the fit calculator
Enter source image dimensions and target box size to get fitted output dimensions.
- 4
Choose contain or cover
Contain letterboxes; cover fills the box by cropping.
Common aspect ratios explained
- 16:9 — standard widescreen for TV, YouTube, presentations, and most monitors
- 4:3 — older TV, iPad screens, and many document-style layouts
- 1:1 — Instagram square posts, profile photos, icons
- 9:16 — vertical video for Instagram Stories, TikTok, and YouTube Shorts
- 21:9 — ultrawide cinema and gaming monitors
- 2.39:1 — anamorphic cinema, the "cinematic" movie look
Frequently asked questions
What is an aspect ratio?+
An aspect ratio is the proportional relationship between width and height, expressed as W:H. A 1920×1080 image has a 16:9 ratio — because both numbers divide evenly by 120. Aspect ratios define the "shape" of a frame regardless of its pixel dimensions.
What is the difference between contain and cover?+
Contain scales an image to fit entirely inside a box, adding letterboxing (empty space) if needed — nothing is cropped. Cover scales an image to fill the box completely, cropping the sides or top/bottom if the aspect ratios don't match.
What aspect ratio should I use for YouTube?+
YouTube recommends 16:9 (widescreen) for standard videos. If your video is in a different ratio, YouTube will add letterboxing or pillarboxing to fill the 16:9 player frame.
What is the aspect ratio of a standard photo?+
Most digital cameras and smartphones shoot at 4:3 or 3:2. DSLRs typically use 3:2 (matching 35mm film). Smartphones with portrait mode commonly use 4:5 or 9:16. Print photo sizes like 4×6 are 3:2.
How do I find the aspect ratio of an image?+
Divide the width and height by their greatest common divisor. For 1920×1080, GCD(1920,1080)=120, giving 16:9. The tool does this automatically in the Image Fit Calculator section.
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