What a megapixel is
A megapixel is simply one million pixels. An image's megapixel count is its width × height in pixels: a photo of 4000 × 3000 pixels holds 12 million pixels — so 12 megapixels. The number measures the fineness of the resolution, how much detail an image can theoretically hold. It says nothing about how good the image looks — more on that below.
How many megapixels you actually need
| Purpose | Megapixels needed | Pixels (approx.) |
|---|---|---|
| Web, social media | 2–3 MP | 2000 × 1500 |
| Print up to A4 / Letter | ~8 MP | 3500 × 2500 |
| Print A3 / poster | ~12 MP | 4200 × 2800 |
| Large format, heavy cropping | 20 MP+ | 5500 × 3600+ |
The takeaway: a standard 12-megapixel phone covers practically every everyday need — from an Instagram post to an A3 poster. The extra megapixels of expensive cameras are mostly headroom for cropping and for large prints viewed up close.
Why more megapixels don't mean better
The biggest misconception: that 108 megapixels make better photos than 12. More megapixels just mean more pixels, not better images. Actual quality is driven far more by other factors:
- Sensor size: a bigger sensor gathers more light — the decisive factor in low light.
- Lens quality: a weak lens can't deliver 108 megapixels of real sharpness, whatever the sensor does.
- Image processing: the software behind the camera shapes the final image substantially.
- Light: good light beats any megapixel count.
That's why many high-megapixel phones combine several pixels into one by default (pixel binning) and effectively deliver around 12 megapixels — on purpose, because it makes better images in low light than 108 individually read, light-starved pixels.
Megapixels aren't dpi
An important distinction that often gets muddled: megapixels count the total amount of pixels; dpi describes how densely you spread them when printing. The same 12-megapixel photo can be printed small and razor-sharp (high dpi) or huge and coarse (low dpi) — the megapixels stay the same, only the print size changes the dpi. The relationship is covered in DPI and PPI explained, and the concrete print math in Is my iPhone photo big enough to print?
The practical conclusion
For everyday shooting: don't chase the highest megapixel number — chase light, framing, and a decent sensor. And when sharing and uploading, the opposite of the marketing promise applies — there you usually want to reduce the megapixels, because 48-megapixel photos are wildly oversized for a web image.
In short
- 12 MP covers almost everything from web to A3 poster.
- More MP ≠ better — sensor, lens, light, and processing matter more.
- Pixel binning trades resolution for cleaner low-light shots.
- Megapixels ≠ dpi — one counts pixels, the other spreads them.