Megapixel
One million pixels, the standard unit for stating a sensor's resolution.
Formula / rule
MP = width × height / 1,000,000
Measured in
MP
In depth
Megapixels determine how large a file can be printed or how far it can be cropped, and almost nothing else. Doubling linear resolution requires four times the pixel count, so the difference between 24 and 30 megapixels is under twelve per cent in each dimension — visually negligible. Sensor size, lens quality and technique all matter more.
Examples in practice
A 24-megapixel file prints comfortably at A2 at 240 ppi without any interpolation.