Guides · 21 August 2026

Why is my photo file so large?

Almost always the megapixels, occasionally the format, and sometimes a setting nobody told you was on. How to tell which, and what each one is worth fixing.

Almost always because it has far more pixels than anything will ever display. A modern phone photo is twelve megapixels or more; a full-screen laptop view shows about two. The rest is weight you are carrying for nothing.

What each cause costs

The megapixel arithmetic

File size follows the number of pixels, and pixel count follows the square of the dimensions. A 4000 × 3000 photo has twelve million pixels. Halve both numbers and 2000 × 1500 has three million — a quarter of the data, before any compression is considered at all.

Now compare that with where the photo is going. A laptop screen shows about two megapixels. An email attachment is usually looked at once, at whatever size the mail client chooses. A website displays perhaps one megapixel. In every one of those, ninety percent of the file was never going to be seen by anyone.

That is why resizing beats compressing so decisively, and it is the step most people skip because “compress” is the word they went looking for.

When the format is the problem

A photograph saved as PNG is the single most expensive mistake in this list. PNG is lossless, so it stores every pixel exactly, and photographs have almost no exactly-repeating pixels for it to work with. The same image that is 2 MB as a JPEG is routinely 25 MB as a PNG, and looks identical.

This happens by accident constantly: screenshots of photos, images pasted into a tool that exports PNG by default, or a “save image” that picked the wrong option. If a file is enormous and ends in .png and shows a photograph, that is the answer.

The reverse mistake is worth naming too. A screenshot or a logo saved as JPEG is both larger and worse than a PNG of the same thing, because JPEG handles hard edges badly. The rule is about the picture, not the file size.

The HEIC surprise

Converting an iPhone photo to JPEG makes it bigger, usually by half again. HEIC compresses roughly twice as efficiently, so the JPEG you converted for compatibility costs you that efficiency. That is a trade rather than a fault, and it is why a folder of converted holiday photos is suddenly larger than it was on the phone.

What to do, in order

1. Resize. Find the largest size the photo will actually be shown at and match it. This removes the most weight for no visible cost, every time.
2. Compress. Quality 82 is where most photographs stop looking different from the original, and typically removes 60–80% of a phone photo because phones save at a conservative default.
3. Change format if you control the destination. WebP is roughly 30% smaller than JPEG at the same quality, for a website you own.
4. Strip the metadata. Worth a kilobyte or two, and worth far more for privacy, since it usually includes where the photo was taken.

Common questions

Does compressing reduce the resolution? No. Compression changes how pixels are stored; resizing changes how many there are. They are different operations, confused because both make the file smaller.

Why did my file get bigger when I compressed it? Because it was already efficiently compressed and the second pass added overhead. A good tool hands back the original in that case rather than the larger version.

Is a 5 MB photo too big to email? For most services, yes in practice — many cap attachments at 10–25 MB total, so a handful of photos exceeds it. Resized to 1600 pixels they will be a few hundred kilobytes each.

Does deleting the metadata make much difference? To size, no — usually a kilobyte or two. To privacy, yes: it typically records the coordinates where the photo was taken.