Stretch vs Resize vs Crop vs Fit: What's the Difference?

The difference between stretch, resize, crop and fit is the math each one uses to reach an exact pixel size. Knowing the formula behind each one makes it obvious which to reach for.

Which Mode to Use: The Short Answer

• Need an exact size and don't mind changed proportions? Stretch.
• Need to scale up or down but keep proportions exact? Resize.
• Need an exact frame with nothing cut off? Fit.
• Need an exact frame with no empty space, and cropping is acceptable? Crop to fill.

Stretch

The source is scaled to the target width and height independently: horizontal and vertical scale factors are calculated separately and neither has to match the other. A 1200×800 image stretched to 1800×800 uses a horizontal factor of 1.5 and a vertical factor of 1. Nothing is cropped and no padding is added; the whole source simply fills the new rectangle, proportions changing along the way.

How far you can push that before it shows depends on the photo: see how to stretch a photo for the percentages.

Resize (proportional)

Only one side is set directly; the other is calculated from the source's original ratio and rounded to the nearest whole pixel. For a 1200×800 source, setting the width to 600 computes a height of 800 × (600 ÷ 1200) = 400. The output is always 600×400, so you cannot land on two arbitrary, unrelated numbers in this mode.

Fit (no cropping)

The scale factor is the smaller of targetWidth ÷ sourceWidth and targetHeight ÷ sourceHeight, so the entire image ends up visible, then it's centered on the target canvas. Fitting a 1200×800 image into a 1200×1200 canvas uses scale = min(1200/1200, 1200/800) = 1, so the image is drawn at its original 1200×800 and centered, leaving 200px of padding above and 200px below.

Crop to fill

The scale factor is the larger of the two ratios, so the scaled image is at least as big as the target in both directions, then the overflow is clipped, centered by default. Cropping that same 1200×800 image to fill 1200×1200 uses scale = max(1200/1200, 1200/800) = 1.5. At that scale the image would be 1800×1200, which is 600px wider than the 1200px target, so 300px is trimmed from the left and 300px from the right to land on the final 1200×1200 output.

Side-by-side comparison

The Same Photo in a Square Frame

The clearest way to see the difference is to give all four modes the same job: turn a 1200×800 photo into a 1200×1200 square. The numbers come from the formulas above, so you can check them by hand.

Fit: the whole vase photo, with padding added.

Crop to fill: no padding, but the edges are gone.

Where Each Mode Goes Wrong

• Stretch bends anything with a known shape. Faces, wheels, logos and lettering are the first things people notice. A circle turns into an oval long before a cloud looks odd.
• Resize refuses to give you two independent numbers. If a form asks for exactly 800×800 and your photo is 1200×800, this mode cannot produce it.
• Fit adds empty space. Whatever fills that space shows up in the final file, so check the preview before you download.
• Crop to fill throws pixels away. A subject near the edge, or text along the border, can disappear without any warning.

Two problems apply to every mode. Enlarging a small photo never adds detail, it only spreads the existing pixels over a bigger area. And these modes change the pixel size, not the file size, so a smaller image can still be too heavy for an upload form.

Which Mode for Which Job

If the job is a specific platform size, the social media image sizes page has ready-made dimensions. If a photo needs space around it without being enlarged, the add padding to image tool does only that.

Combining Modes

You can also use the modes together.

• Crop first, then resize. Cut away what you do not want, such as a stranger at the edge or a strip of empty sky, then resize what is left to the pixel size you need. The result keeps the proportions of the cropped area, so nothing is bent.
• Split a small mismatch between crop and stretch. When the photo's shape is close to the target, a little trimming plus a little stretching can look better than doing all the work with one mode. Check the preview, and see how far you can stretch a photo before it shows.

Common Questions

Is stretching the same as resizing?

No. Resizing keeps the original proportions and changes one side to match the other. Stretching sets width and height independently, so the shape changes.

Which mode keeps the best quality?

None of them adds detail. Quality drops when you enlarge a photo past its original size, and the mode you pick only decides what happens to the shape. Start from the largest original you have.

Does changing the pixel size change the file size?

Usually, but not in a way you can set. Two images with the same dimensions can differ a lot in weight because of content, format and compression. To land under a limit such as 100 KB, use resize image to KB.

Can I change only the width or only the height?

Yes, in Stretch: change one number and leave the other alone. In Resize you set one side and the other follows automatically, so the shape never changes.

Try All Four on One Photo

Try all four on the same file in the image stretcher. Its Compare tab puts the original beside the result. If you need to work out a missing side for a ratio first, the aspect ratio calculator does that arithmetic.