DPI and PPI Calculator
Calculate whether an image has enough pixels for a target print size, screen preview, or export requirement. The calculator keeps pixel count, physical inches, megapixels, print DPI, and diagonal PPI visible together.
Live calculator
DPI and PPI inputs
Enter pixel dimensions and physical output size to calculate print DPI, diagonal PPI, megapixels, and 300 DPI print size.
Calculated resolution
300 DPI
Diagonal PPI
300
Megapixels
7.2 MP
300 DPI print
8 x 10 in
How it works in three quick steps.
Enter pixels
Add image width and height in pixels.
Enter physical size
Add intended output width and height in inches.
Compare results
Review print DPI, diagonal PPI, megapixels, and 300 DPI print size.
Print checks
Estimate whether a raster image can support a selected physical print size.
Screen density
Use diagonal PPI when comparing image dimensions to physical display size.
Export planning
Find the largest 300 DPI print size before resizing or exporting artwork.
DPI and PPI formulas
print DPI = pixels / print inches
PPI = diagonal pixels / diagonal inches
megapixels = width px x height px / 1,000,000
300 DPI width = width px / 300
Use density as a relationship, not a quality promise
Pixel density answers a geometric question: how many image pixels are assigned to each physical inch. Print quality also depends on capture detail, resampling, printer process, substrate, viewing distance, sharpening, and the content of the image.
What the default example reports
The initial 2400 × 3000-pixel image and 8 × 10-inch output are deliberately proportional, so each reported density can be checked by hand.
- Width density
- 2400 pixels / 8 inches = 300 pixels per inch.
- Height density
- 3000 pixels / 10 inches = 300 pixels per inch.
- Limiting print DPI
- The smaller edge density is 300.
- Diagonal PPI
- Matching aspect ratios also produce 300 along the diagonal.
- Megapixels
- 2400 × 3000 / 1,000,000 = 7.2 MP.
- 300-DPI size
- The same pixels map to 8 × 10 inches.
Why the limiting edge matters
When image and print aspect ratios differ, width and height densities are different. The calculator reports the lower edge value because that edge provides fewer pixels per physical inch.
A real workflow must then decide whether to crop, add empty space, or resample. The calculator does not make that composition decision; it exposes the mismatch so it is not hidden behind one averaged number.
DPI and PPI describe related but different systems
PPI usually describes the image or display pixel relationship. Printer DPI describes device dots, and a printer may use several ink dots to reproduce color and tone associated with one image pixel.
The interface uses print DPI as common workflow shorthand for image pixels per output inch, while also displaying diagonal PPI. Keep the distinction in production specifications where printer capability and raster sampling must not be conflated.
Viewing distance changes the decision
A close-viewed photo book and a distant poster can have different useful pixel-density targets. There is no single threshold that guarantees acceptable output for every size, subject, printer, and viewing condition.
Treat 300 as the calculator's explicit comparison target for print-size planning. Ask the print provider for the actual file specification when a job has contractual, archival, exhibition, or publication requirements.
Worked check: enlarge the default image to 12 × 15 inches
- 1Keep the raster at 2400 × 3000 pixels and change physical output to 12 × 15 inches.
- 2Both edges now divide to 200 pixels per inch, so the limiting print result is 200 DPI and the matching diagonal density is 200 PPI.
- 3No pixels were lost merely by changing the intended size, but each inch receives fewer original samples. Decide whether that density suits the output instead of assuming metadata creates detail.
What the calculator cannot evaluate
- Megapixel count does not describe focus, noise, compression, motion blur, color management, sharpening, or whether important detail was captured in the first place.
- Resampling can create additional pixels for a requested dimension, but it estimates values between existing samples and cannot recover scene information that was never recorded.
- Browser zoom changes how large an image appears on screen. It does not alter the file's raster dimensions or the physical print inputs entered into this calculator.
Sources and definitions
- W3C CSS Values: resolution units
Primary web standard reference for dpi, dpcm, and dppx resolution units in CSS.
DPI and PPI questions
What is the difference between DPI and PPI?
PPI usually describes pixels per inch in an image or display, while DPI often describes dots per inch in print output. In practical export conversations the terms are sometimes mixed, so this calculator shows both the physical print-density result and the diagonal pixel-density result.
How do I calculate print DPI?
Divide image pixels by physical print inches. For example, a 2400 pixel wide image printed at 8 inches wide has 300 pixels per inch across that edge. The calculator uses the limiting edge as the practical print DPI.
What is a good DPI for printing?
Three hundred DPI is a common target for sharp photo and document printing, but the right number depends on viewing distance, printer technology, paper, and image content. Posters viewed from farther away can often use lower effective DPI.
Why does diagonal PPI differ from print DPI?
Diagonal PPI uses the diagonal pixel count divided by the diagonal physical size. Print DPI in this calculator checks width and height separately, then reports the smaller edge density because that edge limits the final print resolution.
Can changing metadata increase image quality?
No. Changing a DPI metadata field does not add real pixels. To print larger at the same density, the image needs more pixel data or careful resampling, and resampling cannot recover detail that was not captured.