Calculator · Megapixels
How big
can you
print it?
Megapixels say very little until you turn them into inches. Here is the conversion, at four densities, with the viewing distance that goes with each.
Or pick a common source:
Largest print at 300 DPI
—
| Density | Size | Seen from |
|---|
Megapixels by format, the reference table
Megapixels needed to hold the density at the same aspect ratio. Cropping to a different ratio demands more.
| Format | 300 DPI | 200 DPI | 150 DPI |
|---|---|---|---|
| 4 × 6 in | 2.2 MP | 1.0 MP | 0.5 MP |
| 5 × 7 in | 3.2 MP | 1.4 MP | 0.8 MP |
| 8 × 10 in | 7.2 MP | 3.2 MP | 1.8 MP |
| A4 | 8.7 MP | 3.9 MP | 2.2 MP |
| 11 × 14 in | 13.9 MP | 6.2 MP | 3.5 MP |
| A3 | 17.4 MP | 7.7 MP | 4.3 MP |
| 16 × 20 in | 28.8 MP | 12.8 MP | 7.2 MP |
| A2 | 34.8 MP | 15.5 MP | 8.7 MP |
| 20 × 30 in | 54.0 MP | 24.0 MP | 13.5 MP |
| A1 | 69.7 MP | 31.0 MP | 17.4 MP |
| 24 × 36 in | 77.8 MP | 34.6 MP | 19.4 MP |
Read it this way: a 24 megapixel camera clears A3 easily, just makes 16 × 20 in, and does not hold 24 × 36 in at full density. That is the ordinary ceiling of consumer gear, and the reason upscaling exists.
Viewing distance changes everything
A print is not examined under a microscope. The eye resolves about 5 line pairs per millimetre at 25 cm; at one metre, four times fewer. Useful density follows that law, which allows formats the 300 DPI rule would forbid.
| Use | Distance | Useful density | What it changes |
|---|---|---|---|
| Book, print held in hand | 10 to 16 in | 300 DPI | no leeway |
| Framed on a wall | 3 to 6 ft | 150 to 200 DPI | size doubled |
| Large panel | 10 ft and up | 100 DPI | size tripled |
| Billboard | 30 ft | 30 to 50 DPI | a screen file will do |
Print-on-demand platforms demand 300 DPI because they do not know where the buyer will hang the print. It is a safety margin, not a law of physics.
Short on megapixels?
The workshop rebuilds detail with a neural network and writes the file at 300 DPI. Its interface is in French for now.
Other calculators: DPI calculator, check a file, unit converter.