Pixels & DPI Questions
Resolution math for print dimensions and image files.
20 answers in this topic. Select a question for its dedicated reference page.
01How many pixels is A4 at 300 DPI?
A4 at 300 DPI is 2480 × 3508 px in portrait.
02How many pixels is A4 at 72 DPI?
A4 at 72 DPI is 595 × 842 px.
03How many pixels is A4 at 150 DPI?
A4 at 150 DPI is 1240 × 1754 px.
04How many pixels is Letter at 300 DPI?
US Letter at 300 DPI is 2550 × 3300 px in portrait.
05How many pixels is 4 × 6 at 300 DPI?
A 4 × 6 in photo at 300 DPI is 1200 × 1800 px.
06What does DPI mean?
DPI means dots per inch and describes printer output resolution. Image planning often uses the related PPI measure.
07What is PPI versus DPI?
PPI measures image pixels per inch; DPI measures printer dots per inch. They are related but not identical.
08How do I convert mm to pixels?
Divide mm by 25.4, multiply by the target DPI, then round the final value.
09How do I convert pixels to print size?
Divide each pixel dimension by the intended PPI. The result is inches; multiply by 25.4 for mm.
10How do I calculate effective DPI?
Divide pixel width by print width in inches and pixel height by print height. Use the lower result as the limit.
11Is 300 DPI always required?
No. It is a common target for close-viewed print; printer, paper, screening and viewing distance also matter.
12Is 150 DPI enough for a poster?
It can be for posters viewed farther away. Use the printer’s guidance and inspect a proof when possible.
13What resolution is right for large format?
Use the provider’s specification. Large formats often use lower PPI because they are viewed at distance.
14Does changing DPI change pixels?
Changing metadata alone does not. Resampling changes pixel count.
15Does increasing DPI add detail?
No. It changes intended print size unless the image is resampled.
16What is effective resolution?
It is pixel density after the image is placed at a physical size in a layout.
17Why do calculators differ by one pixel?
They may round at different stages or truncate values. Round only the final result for predictable output.
18How many pixels is 8 × 10 at 300 DPI?
An 8 × 10 in print needs 2400 × 3000 px at 300 DPI.
19How many pixels is 5 × 7 at 300 DPI?
A 5 × 7 in print needs 1500 × 2100 px at 300 DPI.
20What DPI should I send a print shop?
Ask the shop for its file specification. Keep original pixels and plan the effective resolution at final size.