Image Aspect Ratio & Crop Calculator
Calculate pixel crop dimensions, centre crop coordinates, and resize scales for 16:9, 4:3, 1:1, 9:16, and custom aspect ratios without distortion.
Image Dimensions & Target Ratio
Visual Crop & Framing Map
Crop & Scaling Breakdown
About this tool
How to use it
- Select a quick preset (4K UHD, 1080p FHD, 4:3 Photo, 9:16 Reel) or enter your original image width and height in pixels.
- Choose your target aspect ratio preset (16:9 widescreen, 9:16 vertical, 4:3, 3:2, 1:1 square, 4:5 portrait, 21:9 ultrawide) or define a custom ratio.
- Review the maximum center crop pixel box, top/bottom or left/right trim margins, pixel retention percentage, and live visual framing preview.
- Use the companion scale tool to calculate the exact scaled height or width for web publishing, avatars, or video thumbnails without image distortion.
Why it matters
Arbitrary image resizing distorts photos by stretching faces and compressing graphics, while blind cropping accidentally cuts off key focal elements. This tool calculates the exact pixel bounding box and center offsets required to conform any digital image to target social media and display aspect ratios while preserving maximum resolution and native geometry.
When to use it
Use this calculator before cropping photos for Instagram feeds (1:1 or 4:5), YouTube thumbnails (16:9), TikTok/Reels/Shorts videos (9:16), setting CSS background-size: cover coordinates, or preparing prints for standard 3:2 and 4:3 photo frames.
Good to know
Calculations use greatest common divisor (GCD) algorithms for exact ratio reduction and standard Euclidean geometry for center crop bounding coordinates. For video and raster graphics pipelines, all crop coordinates are rounded to the nearest integer pixel to avoid sub-pixel anti-aliasing artifacts.
Common questions
What is the best aspect ratio for Instagram posts and reels?
Use 1:1 (1080×1080 px) for square grid posts, 4:5 (1080×1350 px) for vertical portrait feed posts to maximize screen estate, and 9:16 (1080×1920 px) for Instagram Stories, Reels, and TikTok vertical video.
What is the difference between cropping and scaling an image?
Scaling changes the physical pixel dimensions of an image while preserving its aspect ratio and entire image content. Cropping trims pixels from the edges (top/bottom or sides) to change the image's aspect ratio to fit a different canvas shape without distortion.
How do you calculate aspect ratio from pixel width and height?
Find the greatest common divisor (GCD) of the width and height, then divide both dimensions by that GCD. For example, 1920 and 1080 have a GCD of 120, yielding 1920 ÷ 120 = 16 and 1080 ÷ 120 = 9, which gives the 16:9 ratio.
What is letterboxing and pillarboxing?
Letterboxing occurs when a wider image (such as 16:9) is placed on a taller screen (such as 4:3), adding black horizontal bars to the top and bottom. Pillarboxing occurs when a narrower or vertical image is placed on a wider screen, adding black vertical bars to the left and right sides.
How do I crop a 16:9 4K video frame to 1:1 square without losing quality?
From a 3840×2160 pixel source, create a 2160×2160 pixel crop box centered horizontally. The horizontal offset is (3840 - 2160) ÷ 2 = 840 pixels from each side, retaining 100% of vertical resolution with zero interpolation loss.