Inches to pixels: multiply by the DPI
DPI means dots per inch, and for an image file that is pixels per inch, so inches convert directly: pixels = inches × DPI. A 4-inch width at 300 DPI is 4 × 300 = 1200 pixels.
Decimal sizes work the same way. Letter paper is 8.5 × 11 in: 8.5 × 300 = 2550 and 11 × 300 = 3300, so 2550 × 3300 px. When the result is not a whole number, the calculator rounds to the nearest pixel.
Three common sizes at every DPI
| DPI | 2 × 2 in | 4 × 6 in | 8 × 10 in |
|---|---|---|---|
| 72 | 144 × 144 px | 288 × 432 px | 576 × 720 px |
| 96 | 192 × 192 px | 384 × 576 px | 768 × 960 px |
| 150 | 300 × 300 px | 600 × 900 px | 1200 × 1500 px |
| 200 | 400 × 400 px | 800 × 1200 px | 1600 × 2000 px |
| 300 | 600 × 600 px | 1200 × 1800 px | 2400 × 3000 px |
| 600 | 1200 × 1200 px | 2400 × 3600 px | 4800 × 6000 px |
Photo and print sizes in pixels
Width first, then height. Swap the numbers for landscape: a 6 × 4 in print is 1800 × 1200 px.
| Size | At 300 DPI | At 150 DPI | Megapixels at 300 DPI |
|---|---|---|---|
| 2 × 2 in | 600 × 600 px | 300 × 300 px | 0.36 |
| 3.5 × 5 in | 1050 × 1500 px | 525 × 750 px | 1.58 |
| 4 × 6 in | 1200 × 1800 px | 600 × 900 px | 2.16 |
| 5 × 7 in | 1500 × 2100 px | 750 × 1050 px | 3.15 |
| 8 × 10 in | 2400 × 3000 px | 1200 × 1500 px | 7.2 |
| 8.5 × 11 in (Letter) | 2550 × 3300 px | 1275 × 1650 px | 8.41 |
| A4 (8.27 × 11.69 in) | 2480 × 3508 px | 1240 × 1754 px | 8.7 |
| 11 × 14 in | 3300 × 4200 px | 1650 × 2100 px | 13.86 |
| 12 × 18 in | 3600 × 5400 px | 1800 × 2700 px | 19.44 |
| 16 × 20 in | 4800 × 6000 px | 2400 × 3000 px | 28.8 |
| 18 × 24 in | 5400 × 7200 px | 2700 × 3600 px | 38.88 |
| 24 × 36 in | 7200 × 10800 px | 3600 × 5400 px | 77.76 |
A4 is a metric size, 21 × 29.7 cm, so its pixels are worked out from the centimetres and the inch figures are rounded. For other sizes in cm or mm, use the CM to Pixels Converter.
Posters and large prints
Pixel counts grow quickly with size. A 24 × 36 in poster at 300 DPI needs 7200 × 10800 px, almost 78 megapixels: more than six times the 12.19 megapixels of a 3024 × 4032 px phone photo.
Whether a large print needs the full 300 DPI is up to your print shop, so ask which figure it wants and enter that here. At 150 DPI, 24 × 36 in needs 3600 × 5400 px, a quarter of the pixels.
Shape matters as much as size. 4 × 6 in and 24 × 36 in are both 2:3, while 8 × 10 in and 16 × 20 in are 4:5, so a 2:3 photo has to be cropped to fill an 8 × 10 frame. The Art Print Pack makes files for common frame ratios with crop previews, and the PNG Print Checker shows the effective resolution of a PNG at the print size you choose.
DPI sets the print size, not the pixels
A 600 × 600 px image tagged 300 DPI prints at 2 × 2 in. Change the tag to 600 DPI and it prints at 1 × 1 in; change it to 150 DPI and it prints at 4 × 4 in. The pixels, and the detail in them, stay exactly the same.
Screens ignore the DPI tag. A phone or a website shows those 600 × 600 pixels at whatever size the layout gives them, so an inch on screen has no fixed pixel count.
If only the stored DPI is wrong, the DPI Converter changes it without touching the pixels. If the pixels are wrong, the image has to be resized.
Making a photo at the size you worked out
The calculator does the arithmetic only and never changes an image. To make the file:
- Any size: Resize Image in cm / inch mode takes inches and a DPI, crops or fits the photo, and saves the DPI in the file.
- 2 × 2 in: the 2 × 2 inch resizer is preset to 600 × 600 px at 300 DPI.
- US passport and visa photos: size alone is not enough. The US passport photo page adds a guide for the head height the rules ask for.
- Several photos on one 4 × 6 in sheet: the Passport Photo Maker lays them out with cut guides.
When you print, set the scale to 100% or Actual size and switch off fit-to-page, or the printer may enlarge the image to fill the paper.