Crop Calculator — Effective Megapixels After Crop

Cropping reduces megapixels proportionally to the area removed. Cropping to half the width and height keeps only 25% of the pixels (one quarter of the area). A 24MP image cropped in half becomes 6MP. High-resolution cameras (45MP+) give more headroom for cropping.

Cropping gives the same framing as a longer lens, but with lower resolution and no perspective change. A 50mm crop to 2x gives the framing of 100mm but at quarter the megapixels. It also does not change background compression — only physical distance changes perspective.

For a sharp A4 print at the 300 DPI photo standard you need about 8.7 megapixels (3508×2480px). So a 24MP image can be cropped to roughly 33% of its area and still produce a quality A4 print. Drop to 240 DPI (fine for general wall prints viewed at arm’s length) and A4 needs only about 5.5 megapixels (2806×1984px), giving even more cropping headroom. Higher resolution cameras allow more aggressive cropping.

Effectively yes. If you use a 1.5x APS-C sensor and then crop to half the frame, your effective crop factor is 1.5 x 2 = 3x. A 50mm lens would have an effective FOV of 150mm on full frame.