To give a batch of images the same exact pixel width and height, use Preview on your Mac: open the images together, select them in the sidebar, and apply one width and height in Tools > Adjust Size. For images with different proportions, getting every file to identical dimensions requires stretching or cropping; Preview’s proportional setting avoids distortion but may leave one dimension short of the target. Choose the result you need before saving.

Resize multiple images together in Preview

  1. In Finder, select the image files you want to change. Open them in Preview. If they open in separate windows, use Preview’s File > Open flow to bring them into one window, or use Apple’s documented option to display the images in the same window.

  2. Show the sidebar thumbnails if needed, then select the images in the sidebar. Use Command-A when the window contains only the batch you mean to resize; otherwise select just the intended files.

  3. Choose Tools > Adjust Size. Enter the target width and height and check that the unit menu is set to pixels. Preview supports entering width and height and applying an adjustment to multiple images selected together in the sidebar. Apple’s Preview guide

  4. Decide what should happen to aspect ratio. With Scale proportionally selected, changing one value changes the other to preserve the original proportions. That is suitable when images should not look stretched, but images with different aspect ratios will not all end at the same width and height. To force the exact pair of dimensions, turn off Scale proportionally and set both values; this changes proportions when the source ratio differs from the target.

  5. Keep Resample image selected when changing pixel dimensions. Apple describes turning it off as a way to change dimensions without losing image detail; it does not add or remove pixel data to produce a new pixel size. After setting the values, confirm the adjustment, then save or export the edited images. If the originals matter, first duplicate the files in Finder and resize the copies.

Exact dimensions without stretching

When the source images have different aspect ratios, there are three possible outcomes: preserve the whole image and accept varying dimensions, force the same dimensions and stretch some images, or crop some image area so the remaining content fits the target ratio. These are different edits. Preview documents proportional resizing and cropping as separate operations; it does not describe a batch control that automatically crops every image to fill one exact rectangle. Apple’s Preview guide

For a target of 1200 × 800 pixels, for example, a 3:2 source already has the target ratio, while a square source does not. With proportional scaling, the square image cannot fill 1200 × 800 without either empty space or cropping, and Preview’s proportional size adjustment will keep one dimension below the requested pair. To avoid distortion, crop images to the target ratio first, then resize them. Cropping removes content outside the selected area, so inspect the framing image by image before applying that choice. Preview’s crop operation lets you select and discard part of an image, but do not assume one crop will suit every composition.

Check the batch and avoid common mix-ups

Reopen or inspect a few saved outputs and verify their pixel dimensions in Preview’s Tools > Show Inspector. Check a landscape, portrait, and square source if the batch includes all three; a single sample can hide an aspect-ratio mismatch. Keep a backup until you confirm the dimensions and framing look right.

Finder’s Quick Actions > Convert Image can convert formats or make images smaller using a size choice, but Apple documents no exact custom width-and-height fields there. Use Preview when you need to enter a precise pixel pair. Apple’s Finder Quick Actions guide

Also distinguish pixel dimensions from resolution metadata. Preview’s Resolution field relates to print dimensions and file size; for a web or upload requirement such as 1200 × 800 pixels, set width and height in pixels rather than changing resolution alone. Apple documents changing the resolution field to reduce file size separately from changing image dimensions. Apple’s Preview guide

For an ordinary batch with consistent aspect ratios, Preview’s multi-selection is a direct built-in route to one exact pixel size. If the batch mixes aspect ratios, choose between preserved proportions, stretching, or cropping first; that decision determines whether uniform dimensions also preserve the image content.

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