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About this tool
Find the largest quality print an image supports at any PPI, in inches and centimetres, plus the megapixels a target print size needs.
Print Size From Megapixels Calculator divides an image's pixel dimensions by a target pixels-per-inch figure to give the largest print it supports, in inches and centimetres, and works the calculation backwards to say how many megapixels a chosen print size needs. It also applies the one-arcminute visual acuity limit — required PPI ≈ 3438 ÷ viewing distance in inches — so you can judge whether 300 PPI is genuinely necessary or whether 150 will look identical from where the print will hang.
Open Print Size From Megapixels Calculator on AltFTool — it loads instantly in your browser.
Enter the values you already know.
Fine-tune the options to match your scenario.
Read the result and use it in your planning or reporting.
Pixels to print size, and print size back to the megapixels required.
Uses the arcminute acuity limit instead of assuming 300 PPI is always needed.
Every quality level shown in both units, so lab specs in either system work.
A 24 MP file of 6000 × 4000 pixels prints 20 × 13.3 inches (50.8 × 33.9 cm) at 300 PPI, 25 × 16.7 inches at 240 PPI, and 40 × 26.7 inches at 150 PPI, which is fine for a poster viewed from a metre away.
At 300 PPI you need 4800 × 6000 pixels, which is 28.8 megapixels. At the more common lab default of 240 PPI it drops to 3840 × 4800, or 18.4 megapixels — and at 200 PPI, 12.8 megapixels is enough.
No. 300 PPI matches what 20/20 vision can resolve at about 11 inches, which is why it became the standard for books and handheld prints. A print viewed from three feet only needs about 95 PPI, so large wall pieces are routinely printed at 150 PPI or less.
PPI counts image pixels per inch of print and is what determines detail. DPI counts ink droplets the printer lays down, often 1440 or 2880 on a photo inkjet, and several droplets combine to render one pixel. Send files at the right PPI and let the driver handle DPI.
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