Effects of Crop tool on image dimensions

The Crop tool works differently from resampling. When you crop, you select a region of pixels from the original image. Photoshop calculates the resulting dimensions based on the crop selection size and any values you specify in the Crop tool options. Unlike resampling through the Image Size dialog, cropping doesn't add or remove data to fit preset dimensions. Instead, it isolates existing pixels and recalculates their arrangement based on your specified parameters.

For step-by-step cropping instructions, learn how to crop and straighten photos.

To understand how resolution and pixel dimensions relate to image quality, learn how Image size and resolution affect your work.

Crop tool option fields

Before drawing a crop selection, you can specify values in the Crop tool options bar:

• Width and Height: Enter values with unit abbreviations (px, in, cm, mm, pt, pica). Without a unit, Photoshop defaults to inches.
• Resolution: Enter pixels/inch or pixels/cm.

These fields determine how Photoshop interprets your crop selection and calculates the final image properties. Check the Info panel as you draw your crop selection to see the exact pixel dimensions of the area you're selecting.

Crop scenario reference tables

The following tables show how different combinations of Crop tool options affect the final image. All examples start with a 4 × 4 inch, 100 ppi, 400 × 400 pixel image at 468.8 KB.

Scenario 1: Physical size only (no resolution change)

When you specify only width and height in inches without changing the resolution, Photoshop adjusts the pixel dimensions based on the ratio between the crop selection size and the original image dimensions. Resolution is adjusted to accommodate the pixel-to-inch ratio in your crop area.

In this example, reducing the physical size to half (4 × 2 inches) also reduces pixel dimensions by approximately 50%. At the same time, resolution increases slightly to fit the selected pixels into the specified inches.

Scenario 2: Physical size and resolution

When you specify both physical size in inches and a resolution value, Photoshop changes the pixel dimensions to match your specifications. The resulting image contains exactly the number of pixels needed to fill the specified inches at the specified resolution.

In the first example, reducing physical size by half while doubling the resolution maintains the same pixel dimensions and file size. In the second example, both reducing physical size and increasing resolution result in more total pixels and a larger file. In the third example, reducing both physical size and resolution decreases pixels and the file size.

Scenario 3: Pixel dimensions only (no resolution change)

When you specify pixel dimensions without setting resolution, Photoshop maintains the original image resolution (100 ppi). Physical size adjusts to accommodate the specified pixels at that resolution.

Resolution remains at 100 ppi while physical size scales to fit the number of pixels you specified.

Scenario 4: Pixel dimensions and resolution

When you specify both pixel dimensions and resolution, Photoshop calculates a physical size that accommodates the total number of pixels at the specified pixels per inch. File size changes based on the total pixel count.

Physical size varies based on the pixel-to-resolution ratio you specify. Total pixels and file size depend on your pixel dimension settings.

Scenario 5: Resolution only

When you change only the resolution value, the final image depends entirely on the pixel count in your crop selection. The physical size adjusts to fit the specified resolution of those pixels.

Photoshop uses your crop selection size and specified resolution to calculate physical size and pixel dimensions. The number of pixels in your drawn selection directly determines the final image properties.