Image Resize Calculator

Written byOleh Soloninupdated 5 October 2026

Original width, pixels

Original height, pixels

Set by

Value

Original file size, MB

Only needed to estimate the new size.

Result

New size1920 × 1440
Scale, %48%
Width1,920
Height1,440
Megapixels2.76
Estimated size, MBenter the original file size

File size follows area, not the side

Works out the second dimension when the first changes, gives the scale as a percentage, and estimates what happens to the file size.

The commonest mistake when shrinking images: 'half the size means half the file'. Halving both sides leaves a quarter of the pixels: uncompressed data shrinks fourfold, while a JPEG or other compressed file does not shrink in strict proportion.

You can drive it by any of four values here: the new width, the new height, the long side, or a percentage — and the rest follows with the proportions intact.

How to use

Enter the original size in pixels.
Set the length you want for the longer side.
The other side follows on its own — the proportions are kept.
Enter the original file size if you want an estimate of the result.

What changes when an image shrinks

Each row is a run of this calculator for a 4000 × 3000 image. The percentage is a scale on the side, not on the area.

That is why the file shrinks faster than the percentage suggests: area and pixel count go as the square of the scale. Reducing to 48 percent on the side leaves 23 percent of the pixels — 2.76 megapixels out of twelve.

Runs of this calculator for a 4000 × 3000 image.
Longer side	Size	Scale on the side	Megapixels	Share of pixels
800	800 × 600	20%	0.48	4%
1,920	1920 × 1440	48%	2.76	23%
2,560	2560 × 1920	64%	4.92	41%

What this calculator shows

Both dimensions of the new size, proportions preserved
The scale as a percentage of the original
An estimate of the file size after resizing

What to keep in mind

The size estimate assumes the compression level stays put; in practice JPEG compresses slightly more efficiently at small sizes.
Enlarging adds pixels but not detail: a scale above one hundred percent buys nothing real.

FAQs

How do I resize a photo without distorting it?

Set one side and derive the other from the original proportion. Setting both sides independently stretches the image.

How much smaller does the file get?

Roughly in proportion to the drop in area. Halving each side gives a file about a quarter of the size.

What size should I use for a website?

Size the image for the largest area it will be shown in and for the screen's pixel density: an area 1920 CSS pixels wide at double density needs 3840 pixels, for example.

Can I enlarge an image without losing quality?

Not with ordinary interpolation, which only blurs the pixels already there. Neural upscalers invent plausible detail, but invent it they do.

Why does the file shrink more than the side does?

Because the pixel count falls as the square of the scale. Halve the side and a quarter of the pixels remain — and an uncompressed image shrinks by roughly the same factor.

Can an image be enlarged without loss?

No. There is nowhere for new detail to come from: enlarging only stretches the pixels you have and invents what sits between them. Sharpness does not appear; artefacts do.

Worked example

A photo for the web

Input: 4000 × 3000 → width 1920

Output: 1920 × 1440, which is 48% of the original

Note: The pixel count fell by a factor of 4.3, and the file falls by roughly the same. The side only halved — that gap is the whole source of the confusion.

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Image Resize Calculator

Result

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