Pixel360DPI print size formula
A DPI calculator links three numbers: pixel dimensions, print resolution and physical size. Know any two and you can find the third.
print size (in) = pixels ÷ DPI
pixels needed = print size (in) × DPI
centimeters = inches × 2.54
Worked examples
- 3000×2000 at 300 DPI: 3000 ÷ 300 = 10 in, 2000 ÷ 300 = 6.67 in → 10×6.67 in (25.4×16.93 cm)
- 1920×1080 at 300 DPI: → 6.4×3.6 in (16.26×9.14 cm), so a full HD frame is only snapshot-sized in print
- 6000×4000 at 150 DPI: → 40×26.67 in, large enough for a poster
- A4 at 300 DPI: 210 mm ÷ 25.4 = 8.268 in × 300 = 2480 px; 297 mm ÷ 25.4 × 300 = 3508 px → 2480×3508 px
Pixels needed for common print sizes
Rounded to the nearest pixel. Megapixels are for the 300 DPI size.
| Print size | Pixels at 300 DPI | Megapixels | Pixels at 150 DPI |
|---|---|---|---|
| 4×6 in | 1200×1800 | 2.2 MP | 600×900 |
| 5×7 in | 1500×2100 | 3.1 MP | 750×1050 |
| 8×10 in | 2400×3000 | 7.2 MP | 1200×1500 |
| 8.5×11 in (US Letter) | 2550×3300 | 8.4 MP | 1275×1650 |
| 11×14 in | 3300×4200 | 13.9 MP | 1650×2100 |
| 12×18 in | 3600×5400 | 19.4 MP | 1800×2700 |
| 16×20 in | 4800×6000 | 28.8 MP | 2400×3000 |
| 18×24 in | 5400×7200 | 38.9 MP | 2700×3600 |
| 24×36 in | 7200×10800 | 77.8 MP | 3600×5400 |
| A5 (148×210 mm) | 1748×2480 | 4.3 MP | 874×1240 |
| A4 (210×297 mm) | 2480×3508 | 8.7 MP | 1240×1754 |
| A3 (297×420 mm) | 3508×4961 | 17.4 MP | 1754×2480 |
| A2 (420×594 mm) | 4961×7016 | 34.8 MP | 2480×3508 |
Paper sizes follow the ISO 216 standard for A sizes and the usual US photo sizes in inches. Remember that the ratio of your image may not match the paper: a 3:2 camera image fits 4×6 exactly but must be cropped for 8×10. Check with the aspect ratio calculator before you order.
Why 300 DPI for photos and 150 DPI for posters?
300 DPI is the long-standing standard for photo prints and magazines. At normal reading distance it is generally considered fine enough that individual pixels are not visible. Going higher rarely makes a visible difference for photographs.
Posters, banners and signs are viewed from several feet away, so detail at 300 DPI is wasted. 150 DPI is a common target, and very large formats such as billboards can use far less. Your print shop’s spec sheet is the final word.
DPI vs PPI: the mixed-up terms
Strictly, PPI (pixels per inch) describes a digital image or a screen, and DPI (dots per inch) describes the ink dots a printer places. An inkjet may use many dots to render one image pixel. In practice, photo labs, Photoshop and most guides say “300 DPI” when they mean 300 image pixels per inch, and that is how this calculator uses the term. For screens, use the PPI calculator instead.
Common mistakes
- Changing the DPI field and expecting more detail. Without resampling, the pixels stay the same; only the reported print size changes.
- Upscaling to hit 300 DPI. Enlarging a small image meets the number but adds no real detail. A clean 200 DPI print often beats an upscaled 300 DPI one.
- Forgetting bleed. Many printers want extra bleed on each edge, typically 3 mm or 0.125 in. Add it to the print size before calculating.
- Ignoring aspect ratio. Pixels that fit the area can still be the wrong shape for the paper.
Frequently asked questions
How many pixels do I need for an 8×10 print?
At 300 DPI you need 2400×3000 pixels (8 × 300 by 10 × 300), about 7.2 megapixels. At 150 DPI, 1200×1500 pixels is enough for a print viewed from a little farther away.
Does changing the DPI setting change image quality?
No. Changing only the DPI value in an image’s metadata does not add or remove pixels. It just changes the print size the file reports. Quality only changes if you resample, which alters the pixel count.
Is 72 DPI correct for web images?
DPI has no effect on how an image displays on screen. Browsers show images by their pixel dimensions, so a 1200px wide image looks the same at 72, 96 or 300 DPI. The 72 DPI web convention is a leftover from early Mac displays.
What DPI do I need for a large poster?
Posters and banners are usually seen from a distance, so 150 DPI is common and many printers accept 100 DPI or less for very large formats. Ask your print shop for its minimum before exporting.
How big can I print a 12 megapixel photo?
A 4032×3024 photo (about 12 MP) prints at 13.44×10.08 inches at 300 DPI, or about twice that in each direction at 150 DPI.