Megapixel Calculator
Calculate megapixels from any width and height. See the resolution, crop factor, and print size behind common camera and phone specs.
Megapixels are a camera specification, not a quality score, and the number only means something next to the sensor and lens behind it. This calculator converts dimensions both ways, so you can check what a sensor size spec means in pixels, and it pairs that with the print size and crop factor that the same pixels imply.
How it works
The calculation
Megapixels is a count, not an area, so the conversion is one multiplication and one division. The useful part is what the number implies: combined with the aspect ratio it gives you the print size, and combined with the sensor size it gives you the crop factor.
megapixels = (width × height) / 1,000,000
Megapixels in common devices and use cases
Megapixel counts are quoted for cameras, phones, and screens, and each use case needs a different amount. A 12 MP phone has more than enough for a framed print, while a large poster needs more than a phone typically produces.
| Megapixels | Example resolution | Sharp print at 300 DPI | More than enough for |
|---|---|---|---|
| 2 MP | 1,600 × 1,250 | 5.3 × 4.2 in | Social posts and small web images |
| 8 MP | 3,264 × 2,448 | 10.9 × 8.2 in | Web use, small prints, video stills |
| 12 MP | 4,000 × 3,000 | 13.3 × 10 in | 8×10 prints, most social platforms |
| 24 MP | 6,000 × 4,000 | 20 × 13.3 in | A3 prints and moderate cropping |
| 45 MP | 8,256 × 5,504 | 27.5 × 18.3 in | A2 prints and heavy cropping |
| 100 MP | 12,000 × 8,000 | 40 × 26.7 in | Large prints where detail survives resizing |
Why megapixels do not measure quality
A megapixel counts pixels and says nothing about whether each one carries useful information. Sensor size, lens quality, and the amount of light available determine that. A 12 MP phone with a small sensor often captures less usable detail than a 8 MP camera with a large one, because the pixels on the larger sensor gather more light. This is why two devices with identical megapixel counts produce visibly different images.
- Sensor size sets how much light each pixel receives, which drives noise and detail.
- Lens quality sets how sharp the image is across the frame, independent of pixel count.
- Pixel size is the sensor area divided by the megapixels, so more megapixels on the same sensor means smaller pixels.
Crop factor and the pixels you keep
A crop is a digital zoom, and it costs pixels. Cropping a 24 MP frame to half its width and height leaves 6 MP, which is the same amount of detail a 6 MP camera would have recorded. Knowing the megapixel budget of your file before you crop tells you how much room you have to work with.
- Half width and half height gives exactly one quarter of the pixels.
- A 45 MP file cropped to 24 MP looks like a 24 MP file, because it contains that much information.
- To keep as much as possible, crop rather than shrink, and check the result with the print size calculator.
Frequently asked questions
How do I calculate megapixels?
Multiply width by height in pixels and divide by one million. A 4,000 by 3,000 image is 12 megapixels, which is the 12 MP figure quoted for many phones.
How many megapixels do I need for a print?
At 300 DPI, an 8 by 10 inch print needs about 7.2 megapixels, and a 4 by 6 needs about 2. A 20 by 30 inch poster at 150 DPI needs about 27 megapixels, which is more than most phone cameras produce.
Does more megapixels always mean better photos?
No. Megapixels measure pixel count only. Sensor size, lens quality, and light gathering determine how much detail those pixels actually capture, and two 12 MP phones can produce very different images.
How do I go from megapixels back to pixels?
You need a shape as well as a total. A 12 MP image could be 4,000 by 3,000, 3,464 by 3,464, or 6,000 by 2,000, and each behaves differently when printed. Use the aspect ratio calculator to apply the shape you want.