Treating megapixels as a sharpness rating, when a badly focused 48 MP shot holds less real detail than a crisp 12 MP one.
Resolution and scaling
Megapixel
Also called mp, megapixels or mega pixel. Here is what it means, when it changes what you export, and what people get wrong.
Resolution and scalingRuns on your deviceUpdated 10 August 2026
The short answer
A megapixel is one million pixels. To get an image's megapixel count, multiply its width in pixels by its height and divide by 1,000,000, so a 4000 x 3000 photo is 12 MP. It measures how much data an image holds, not how sharp or well exposed it is.
Updated
The short version
Megapixel at a glance
| Quick fact | Detail |
|---|---|
| One megapixel | 1,000,000 pixels |
| Formula | width x height / 1,000,000 |
| 12 MP looks like | 4000 x 3000 px |
| Shopify maximum | 5000 x 5000 px, 25 MP, under 20 MB |
| 25 MP decoded in memory | About 100 MB at 8 bits per channel |
Slide the table sideways to see every column.
How do you work out megapixels from pixel dimensions?
Multiply the two dimensions and divide by a million. A few common cases:
- 1000 x 1000 = 1,000,000 = 1.0 MP
- 1600 x 1600 = 2,560,000 = 2.56 MP
- 2048 x 2048 = 4,194,304 = 4.19 MP
- 1920 x 1080 = 2,073,600 = 2.07 MP
- 4000 x 3000 = 12,000,000 = 12 MP
- 5000 x 5000 = 25,000,000 = 25 MP
Notice how fast it climbs. Doubling both dimensions multiplies the megapixel count by four, which is why a jump from 2048 px square to 4096 px square is a much bigger change than it sounds.
Why do platforms cap megapixels rather than width?
Because memory and processing cost track total pixels, not the longest edge. Shopify accepts images up to 5000 x 5000 px, which it describes as a 25 MP ceiling, with the file itself under 20 MB. A 25 MP image with four 8-bit channels needs roughly 100 MB of memory once decoded, regardless of how small the compressed file was. A single width limit would let a 20000 x 200 px panorama through while blocking a modest square, so the pixel total is the fairer measure.
Do more megapixels mean a better photo?
No. Megapixels tell you how finely the scene was sampled, not how good the sample was. Lens quality, focus, lighting, sensor size and compression all decide whether those pixels carry real detail. A soft or slightly shaken 48 MP phone shot can hold less usable information than a sharp 12 MP one. Where extra megapixels genuinely help is headroom: they let you crop hard, straighten a shot, or export the same master at several sizes without ever enlarging.
What people get wrong about megapixel
Each one is a real failure mode, not a style preference.
Upscaling a 2 MP image to 12 MP and assuming it now satisfies a 12 MP requirement in any meaningful way.
Confusing megapixels with file size; two 12 MP JPEGs can differ tenfold in bytes depending on quality settings and subject.
Questions people ask
Megapixel, answered
The follow-up questions people search for once they have the definition.
How many megapixels is 1920 x 1080?
About 2.1 MP. 1920 x 1080 = 2,073,600 pixels. Full HD sounds large because it fills a screen, but as a still image it is small: most marketplace guidance asks for 1600 px or more on both sides, and 1080 px falls short on the shorter edge.
Is 12 MP enough for an online store?
Comfortably. A 12 MP camera file at 4000 x 3000 px crops to a 3000 x 3000 square, which exceeds Etsy's 2000 px guidance, eBay's recommended 1600 x 1600 px and Shopify's 2048 x 2048 px display size. You will be resizing down, not up.
How many megapixels do I need to print?
At 300 pixels per inch, an 8 x 10 inch print needs 2400 x 3000 px, which is 7.2 MP. A 12 MP file covers that with room to crop. Larger prints are usually viewed from further away, so 150 to 200 ppi is often acceptable above A3.
Does cropping reduce megapixels?
Yes, in direct proportion to the area you keep. Cropping to the middle half of the width and the middle half of the height leaves a quarter of the pixels, so a 12 MP photo becomes 3 MP. This is why heavy cropping and large output sizes pull against each other.
Same cluster
More from the glossary
Neighbouring entries, so every term in the set is one hop from every other.
Model quantisation
Quantisation stores and computes a model's weights at lower numeric precision, typically dropping from 32-bit floats to 16-bit floats or 8-bit integers.
Matte
A matte is a greyscale image that records how opaque every pixel of a subject is: white for fully solid, black for fully transparent and grey for everything in between.
Motion blur
Motion blur is the smearing you get when the subject or the camera moves while the shutter is open.
From the studio
Tools that do this
Each one runs on your own device, so the photo stays where it is.
Sources
Where the facts on this page come from. Every link opens the specification, standard or documentation the claim was read at.
Keep reading
Elsewhere on Photomop
Platform image rules
Image size, file type and background rules for 22 selling platforms, each one sourced.
Read itConvert image
JPG, PNG, WebP and AVIF, with an honest answer about HEIC and alpha.
Read itAll the tools
The whole toolbox in three families, with what each one needs before it can run.
Read itOn-device privacy
The pipeline in five steps, what leaves your device, and how to check it yourself.
Read it
Now do it to a photo
Photomop is a photo studio that runs on your own device. Resize, crop, compress, convert, batch edit, remove a background and change one all work in the browser tab you are reading this in, at full resolution and with no watermark. The on-device page shows you how to check that the photo stays put.