What if my crop tool doesn't have a 4:5 or 16:9 preset?

You can manually set the crop area to the correct proportions by calculating the dimensions. For example, for 4:5, make the width 4 units and height 5 units (or a multiple, like 400 × 500 pixels). Many tools show the aspect ratio as you drag.

Can I crop to 3:2 aspect ratio?

Yes. 3:2 matches most camera sensors. To crop to 3:2, set the width to 3 units and height to 2 units. For a width of 1200 pixels, the height would be 1200 × 2 ÷ 3 = 800 pixels.

Why does cropping a JPG reduce quality?

When you crop and save a JPG, the image is re-encoded using lossy compression. For lossless cropping, use jpegtran with crop coordinates that align to 8- or 16-pixel blocks.

Do I need to crop before resizing?

Yes. Cropping changes the aspect ratio. Resizing changes the pixel dimensions but keeps the current ratio. If you resize first, you may distort the image or end up with the wrong proportions.

Crop a JPG to 1:1, 4:5 or 16:9 (Exact Ratios)

Cropping a JPG to a specific aspect ratio such as 1:1, 4:5, or 16:9 starts with one fact: aspect ratio is width divided by height. A 1:1 ratio is a square. A 4:5 ratio is portrait orientation. A 16:9 ratio is widescreen, and 3:2 matches most camera sensors. Learn the maths behind these ratios and you can use built-in crop tools to make images fit feeds, banners, and thumbnails. Crop first, then resize to exact pixel dimensions. The methods below give precise results without guesswork.

Understanding Aspect Ratio Maths

Aspect ratio is width divided by height. The notation 1:1 means width and height are equal, producing a square. For 4:5, the width is 4 units for every 5 units of height, a portrait orientation. For 16:9, the width is 16 units for every 9 units of height, the standard widescreen format. The ratio 3:2 is common for many camera sensors.

To find the missing dimension when you know one side and the target ratio, multiply the known dimension by the second number of the ratio, then divide by the first number.

A width of 1080 pixels at 4:5 becomes 1080 × 5 ÷ 4 = 1350 pixels tall.
A width of 1920 pixels at 16:9 becomes 1920 × 9 ÷ 16 = 1080 pixels tall.

Working from height works too. For a 16:9 image that is a certain height, you can calculate the corresponding width.

Cropping Vs. Resizing

Resizing keeps the aspect ratio when the maintain aspect ratio option is on. Changing the ratio requires cropping. If you resize a 4:5 image to 16:9, the image distorts. Cropping removes parts of the image to achieve the new ratio, then you resize to the exact pixel dimensions you need. Always crop first, then resize.

Crop a Photo to 1 -1 (Square)

Square Crop in iPhone Photos

Open the image in iPhone Photos. Tap Edit, then Crop. Tap the aspect ratio button and select Square (1:1). Adjust the crop frame if needed, then tap Done.

Square Crop in macOS Preview

Open the image in macOS Preview. Drag a selection on the image to define the crop area. Go to Tools and select Crop, or press Cmd+K. The selection becomes the new image.

For a square result, make sure your selection is equal in width and height. Check the pixel dimensions in the selection tool info bar.

Crop to 4 -5 Aspect Ratio Pixels

To crop an image to a 4:5 aspect ratio, calculate the correct dimensions. For a final image 1080 pixels wide, the height must be 1080 × 5 ÷ 4 = 1350 pixels. In your editing software, use the crop tool to select an area that matches this proportion. Most crop tools show the aspect ratio as you drag. Enter the ratio manually if the tool supports it.

4:5 Crop in iPhone Photos

In iPhone Photos, after tapping Edit and Crop, tap the aspect ratio button. The presets include 4:5. Select it and adjust the crop frame to choose which part of the image to keep.

4:5 Crop in macOS Preview

In Preview, drag a selection while holding Shift to constrain proportions. Preview does not have a 4:5 preset. Calculate the dimensions and drag the selection manually, then crop with Cmd+K.

Crop to 16 -9 Image Size

For a 16:9 crop, the width is 16 parts and height is 9 parts. A common 16:9 image size is 1920 pixels wide by 1080 pixels tall. To crop any image to 16:9, calculate the required height from your desired width, or vice versa. For a width of 1920: height = 1920 × 9 ÷ 16 = 1080. For a given height, you can calculate the corresponding width.

16:9 Crop in iPhone Photos

In iPhone Photos, the aspect ratio button includes a 16:9 preset. Select it and adjust the crop frame to choose the area you want.

16:9 Crop in macOS Preview

In Preview, set the selection to 16:9 by dragging while holding Shift. The exact ratio may require manual adjustment. Use the info panel to check width and height as you drag.

Lossless Cropping with Jpegtran

Cropping a JPG and saving it normally re-encodes the image, which can reduce quality. For lossless cropping, use jpegtran. This tool crops without re-encoding, but only when the edges of the crop area align to 8-pixel or 16-pixel blocks. Adjust your crop coordinates to match these block boundaries. The result is a JPG that has not been recompressed, preserving the original quality.

Resizing After Cropping

After cropping to the correct aspect ratio, resize the image to exact pixel dimensions for its use, such as a feed, banner, or thumbnail. After cropping to 16:9, resize to 1920 × 1080 pixels. Use your image editor's resize function and keep the maintain aspect ratio option on so the dimensions stay correct. Remember the order: crop first, then resize.