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Aspect Ratio Crop Calculator

Reviewed by the CalculatorHub team, edited by James Graham. Standard ratio constraint formula. Last verified 15 June 2026.

Cropping an image to a specific aspect ratio is a common need in photography and video production, from preparing images for social media to fitting a print format. This calculator finds the largest rectangle of your target aspect ratio that fits inside your original image dimensions. Enter the original pixel dimensions and your target ratio (as width:height numbers) to get the exact crop dimensions in pixels, along with the number of pixels cropped from each edge for a centered crop.

Width of your source image in pixels.
Height of your source image in pixels.
For 16:9, enter 16. For 4:3, enter 4. For 1:1, enter 1.
For 16:9, enter 9. For 4:3, enter 3. For 1:1, enter 1.
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Aspect ratio crop formula

If source_ratio > target_ratio (source is wider):
crop_height = original_height, crop_width = original_height x (target_W / target_H)
If source_ratio < target_ratio (source is taller):
crop_width = original_width, crop_height = original_width x (target_H / target_W)

Example: 6,000 x 4,000 px (3:2 ratio) cropped to 16:9. Source ratio 1.5, target 1.778 (16/9). Source is narrower (taller proportionally). Crop width = 6,000, crop height = 6,000 x (9/16) = 3,375 px. Left/right offset = 0. Top/bottom offset = (4,000 - 3,375) / 2 = 312 px each.

Common aspect ratios

  • 1:1 (square) for Instagram square posts
  • 4:5 (portrait) for Instagram portrait posts
  • 16:9 (widescreen) for YouTube, TV, most video
  • 9:16 (vertical) for TikTok, Instagram/YouTube Shorts
  • 3:2 (35mm still film) for most DSLR sensors
  • 4:3 (standard TV / MFT) for Micro Four Thirds cameras

Aspect ratio crop calculator: frequently asked questions

What is aspect ratio and why does it matter for cropping?

Aspect ratio is the ratio of width to height. Common ratios include 16:9 (widescreen video), 4:3 (traditional TV), 1:1 (square, Instagram), and 3:2 (35mm film still). When cropping to a different ratio, one dimension may need to be reduced to maintain the target proportions.

How is the crop size calculated?

If the target ratio is W:H, the maximum crop that fits inside an original of width Wo and height Ho is: constrained by whichever dimension hits the boundary first. If Wo/Ho is greater than W/H (source is wider), limit by height: crop_width = Ho x (W/H), crop_height = Ho. Otherwise, limit by width: crop_width = Wo, crop_height = Wo x (H/W).

What aspect ratio should I use for social media?

Instagram square: 1:1. Instagram portrait: 4:5. Instagram landscape: 16:9. YouTube thumbnail: 16:9. Twitter/X: 16:9 or 2:1. Facebook: 16:9 or 1.91:1. TikTok: 9:16 (vertical).

Does cropping reduce resolution?

Yes. Cropping removes pixels. If you crop a 6,000 x 4,000 pixel image to 4:3 (a 5,333 x 4,000 crop), you lose 667 pixels of width. The resulting file has fewer pixels, so printing it at the same size as the original will be slightly lower resolution.

How do I crop without losing the subject?

Center your crop box on the subject, then check that the subject fits within the crop boundaries. If the crop is significantly smaller than the original, consider using a camera preset for that ratio at capture time to compose for the final ratio from the start.

Official sources

  • ITU-R BT.709: Parameter values for HDTV (defines 16:9 standard). ITU.int.
  • SMPTE ST 2067: Interoperable Master Format (IMF), covers aspect ratio metadata. SMPTE.org.

Reviewed by the CalculatorHub team, edited by James Graham, 15 June 2026. See our methodology.