Does cropping reduce image quality or file size?

What cropping does to the pixels

The pixels inside the crop stay exactly as they were. The ones outside are thrown away. So the picture does not get blurry from the crop itself. It gets smaller: fewer pixels, fewer megapixels.

A 4032 x 3024 phone photo has about 12.2 megapixels. A square crop of it, 3024 x 3024, has about 9.1 megapixels. A crop of a quarter of the picture keeps about 3 megapixels.

Check a crop before you export

1. 01Check the cropped width and height in pixels, not just the file size in megabytes.
2. 02Compare both dimensions with your destination. A 1600 x 1200 crop cannot fill a 2000 x 2000 square without enlargement and more cropping.
3. 03Inspect the result at 100 percent zoom, then at the size your customers will see it. These are different checks.
4. 04Export once from the original. Compare the exported file with the editor preview, because JPEG compression can introduce artifacts even on the first save.

How much can you crop? A table

Whether a crop is too small depends on where it goes. For a print, divide the pixels by the print density: at 300 pixels per inch, a common target for sharp prints, every inch needs 300 pixels. For a screen or a marketplace, compare with the size the platform asks for.

• No crop

  Pixels left

  4032 x 3024 (12.2 MP)

  Sharp print at 300 PPI

  13.4 x 10.1 in

  Enough for

  Any marketplace, 8x10 print

• Square

  Pixels left

  3024 x 3024 (9.1 MP)

  Sharp print at 300 PPI

  10.1 x 10.1 in

  Enough for

  Etsy, Amazon, Shopify 2048 square

• Half the width and height (a quarter of the picture)

  Pixels left

  2016 x 1512 (3.0 MP)

  Sharp print at 300 PPI

  6.7 x 5.0 in

  Enough for

  eBay and Amazon minimums, a 4x6 print. Too small for Etsy's 2000 px

• A quarter of the width and height

  Pixels left

  1008 x 756 (0.8 MP)

  Sharp print at 300 PPI

  3.4 x 2.5 in

  Enough for

  eBay's 500 px minimum, Amazon's 1000 px only just

So a square crop of a phone photo still meets every marketplace size we track. Cropping to half the width is fine for eBay, Amazon and small prints, but not for Etsy or Shopify's 2048 px. A tight crop of a small detail is where it stops working everywhere. For print sizes, see how to crop a photo to 4x6 or 8x10.

Does cropping reduce file size?

Usually, yes. Fewer pixels means less to store, so a cropped JPEG is normally smaller than the original. It is not guaranteed, though. If your editor saves the crop at a higher JPEG quality than the camera did, or as a PNG, the file can stay the same size or even grow. If you want a smaller file without losing more of the picture, resize or compress it after the crop. See crop vs resize.

Digital zoom is a crop too

Zooming past your phone camera's real lenses does not add detail. It crops the middle of the sensor and enlarges it, which is why digital zoom looks soft. Shopify's photography guide says the same: digital zoom simply crops the image and reduces quality. Step closer, or shoot wide and crop later, where you can choose the frame.

Where quality is really lost

• Fewer pixels for the same display size. If you show a small crop at the size of the whole photo, the picture looks soft, because each pixel is stretched. Keep crops large enough for where the picture will be shown.
• Re-saving as JPEG. Most editors decode and re-encode a JPEG when you export. Even one export can introduce loss; repeated exports can add more. Export once from the original and inspect the result.
• Enlarging afterwards. Scaling a crop up creates pixels that were never there. It is the main cause of soft results.

How to crop without losing quality

1. 01Shoot at the highest resolution your camera offers.
2. 02Crop a copy, never the only original.
3. 03Crop once. Do not crop a crop.
4. 04Do not enlarge the result. Choose a crop that is already big enough.
5. 05Export once, as a JPEG at a high quality such as 85 to 92, or keep a lossless PNG while you work.

Some tools can crop a JPEG without re-encoding it, but only along block boundaries, which are multiples of 8 or 16 pixels. That is rare in everyday apps.