Print Size & DPI Calculator
Convert between pixel dimensions, print size and DPI, and see how big you can print before quality drops.
Fill in the fields above — everything recalculates as you type.
- Print size (inches)
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- Print size (cm)
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- Pixel dimensions
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- Resolution
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- Megapixels
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- Aspect ratio
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- Print quality
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Standard print sizes at 300 DPI
“Your image” compares the pixel dimensions above with what each size needs at the current resolution. Rotating the print to match your orientation counts as a fit.
| Print size | Inches | Centimetres | Pixels needed | Your image |
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How it works
Print resolution is plain division: inches = pixels ÷ DPI. Turn it around and you
get the other two forms this calculator uses — DPI = pixels ÷ inches and
pixels = inches × DPI. Centimetres come from the exact inch definition
(1 in = 2.54 cm), so a 3000 × 2000 px photo at 300 DPI prints at exactly
10.00 × 6.67 in, or 25.40 × 16.93 cm. When the width and height work out to different
resolutions — because the print shape does not match the image shape — the lower of the two
is the one that limits sharpness, so that is the number used to judge quality.
Strictly speaking DPI (dots per inch) describes a printer’s ink dots and PPI (pixels per inch) describes an image file, but print shops and photo labs use the terms interchangeably for “how many image pixels land in one inch of paper”, and that is what is calculated here. As a rule of thumb 300 DPI is the photo-lab standard, 240 DPI is still visibly sharp, and big posters viewed from a few metres away look fine at 150 DPI or less. The reference table converts the standard photo, US and ISO A sizes at whatever resolution you set — A4 at 300 DPI is the familiar 2480 × 3508 px. Everything is computed in your browser with plain JavaScript: nothing is uploaded, there are no ads and no sign-up.
Frequently asked questions
How do I calculate DPI from pixels and print size?
Divide the pixel dimension by the printed dimension in inches: DPI = pixels / inches. A 1200 x 1800 px photo printed at 4 x 6 in works out at 1200 / 4 = 300 DPI across and 1800 / 6 = 300 DPI down. If the two numbers differ because the print shape does not match the image shape, the lower one is what limits sharpness.
How many pixels do I need for an 8 x 10 inch print?
Multiply each side by the resolution you want: 8 x 300 = 2400 and 10 x 300 = 3000, so 2400 x 3000 px (7.2 megapixels) at the 300 DPI photo-lab standard. At 240 DPI you would need 1920 x 2400 px, and a poster viewed from a few metres away still looks fine at 150 DPI (1200 x 1500 px).
Is DPI the same as PPI?
Strictly no — DPI counts a printer's ink dots per inch and PPI counts image pixels per inch — but photo labs and print shops use the terms interchangeably for how many image pixels land in one inch of paper. That is the number this calculator works with, so entering 300 gives the same answer whichever label your printer uses.