How pixel-to-size conversion works
DPI (Dots Per Inch) is the number of pixels packed into one printed inch. Dividing pixel count by DPI gives the length in inches, and since 1 inch is exactly 2.54 cm, that converts directly to centimeters and millimeters.
- pixels — the image's width or height in pixels
- dpi — print resolution — 300 for standard print, 72 for web
Common values
| Pixel count (px) | Real size (cm) |
|---|---|
| 300 px | 2.54 cm |
| 750 px | 6.35 cm |
| 1,500 px | 12.70 cm |
| 3,000 px | 25.40 cm |
| 4,500 px | 38.10 cm |
| 6,000 px | 50.80 cm |
| 9,000 px | 76.20 cm |
| 15,000 px | 127.00 cm |
| 30,000 px | 254.00 cm |
More detail
Why the same pixels print at different sizes
A 3000-pixel-wide image prints smaller at 300 dpi than at 72 dpi, because DPI is a density: more dots per inch packs the same pixel count into less paper. Web images are typically exported at 72 dpi; print photos usually need 300 dpi or higher.
Practical tip. Before sending a photo to print, check its pixel dimensions against 300 dpi. A full-page A4 print (21 × 29.7 cm) at 300 dpi needs about 2480 × 3508 pixels.
Frequently asked questions
How many cm is a 3000px image printed at 300 dpi?
inch = 3000 ÷ 300 = 10 inches, and cm = 10 × 2.54 = 25.4 cm. Enter 3000 pixels and 300 dpi above to see the same result.
Why do web (72 dpi) and print (300 dpi) images come out different sizes?
Lower DPI means fewer dots packed per inch, so inch = pixels ÷ dpi grows larger — the same pixel count prints bigger. A 1000px image is about 35.3 cm at 72 dpi but only about 8.5 cm at 300 dpi.
How many pixels do I need for a full A4 print?
A4 is 21 × 29.7 cm. At 300 dpi that works out to roughly 2480 × 3508 pixels (cm ÷ 2.54 × dpi, the reverse of this calculator's direction).
What DPI should I use if I don't know the target printer?
The DPI field defaults to 300, the standard for photo-quality print. Entering 0 or a negative number leaves the result as "—" since the division isn't defined.