The photo aspect ratio calculator helps you resize or crop images while maintaining proportions. Enter original dimensions and a target width, height, or aspect ratio to get the correct output dimensions instantly.
Calculate Aspect Ratio
Original Dimensions
Target: Scale to Known Width or Height
Or Crop to Common Aspect Ratio
How to Use the Aspect Ratio Calculator
Enter your original image dimensions (width × height in pixels), then either enter a target width/height to scale proportionally, or select a target aspect ratio to see the crop dimensions.
Understanding Aspect Ratios
Most DSLRs and mirrorless cameras shoot 3:2 (6000×4000 on a 24MP sensor). Smartphones typically shoot 4:3. If you want a square Instagram post from a 3:2 image, you'll need to crop — either 100% of the height (center square crop) or a slightly wider area.
Cropping vs. Letterboxing
When changing aspect ratios, you have two choices: crop (remove pixels from sides or top/bottom) or letterbox (add black bars). For social media, cropping is standard. For film/video delivery, letterboxing is often required to maintain the full frame.
FAQ
What is aspect ratio in photography?
Aspect ratio is the proportional relationship between a photo's width and height, expressed as W:H. Common ratios are 3:2 (DSLR full-frame), 4:3 (Micro Four Thirds, most smartphones), 1:1 (square), and 16:9 (widescreen/video). The same ratio can produce images of vastly different sizes.
How do I maintain aspect ratio when resizing?
To maintain aspect ratio, multiply both dimensions by the same scale factor. If your original is 6000×4000 (3:2 ratio) and you want a 1200px wide image, divide 1200/6000 = 0.2 scale factor, then new height = 4000 × 0.2 = 800px. This calculator does this automatically.
What aspect ratio should I use for printing?
4×6 prints use 3:2 ratio, 5×7 prints use 5:7, 8×10 prints use 4:5, and 4×5 (or 8×10) are common for portraits. If your camera shoots 3:2 but you want 5×7 prints, you'll need to crop approximately 1.4% from the long edge.
What is the best aspect ratio for Instagram?
Instagram supports 1:1 (square), 4:5 (portrait, fills more screen — recommended for maximum engagement), and 1.91:1 (landscape). For Stories and Reels, use 9:16. Portrait posts (4:5) get more screen real estate in feeds.
Is this tool free?
Yes, completely free with no signup required. All calculations happen in your browser.