DPI / PPI Calculator
Work out dots or pixels per inch from an image's pixel count and physical size, plus the print width at 300 DPI, with a 3000-pixel example.
Results
DPI / PPI
- For 300 DPI print width
- 10 in
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Formula / how it works
DPI/PPI = pixels / inches.
Detailed guide
What it is, how to use it, how to read the numbers, common mistakes, a worked example, formulas, and FAQs.
What this calculator is
PPI describes how many pixels fit in each inch of an image or screen, while DPI describes how many ink dots a printer lays down per inch. In practice people use the terms loosely. For print, higher density gives sharper detail, and 300 is a widely used target for photographs viewed up close. This calculator divides the pixel count along one edge by the physical size of that edge. It also shows the largest print width that keeps 300 DPI. Posters and billboards are viewed from a distance and are often printed at much lower densities. The pixel count is fixed, so enlarging a print lowers its density.
When to use / who it helps
- You want to know whether a photo is big enough to print at a size.
- You are preparing a file for a printer.
- You are comparing screen sharpness.
- You are choosing a camera resolution.
- You are checking an image before enlarging it.
How to use
Steps
- Enter the number of pixels along one edge.
- Enter the physical length of that edge in inches.
- Read the DPI or PPI.
- Read the print width that keeps 300 DPI.
- Repeat for the other edge to check both.
- Convert centimetres to inches first by dividing by 2.54.
How to interpret results
- A higher DPI means finer detail at that size.
- 300 DPI is a common target for close-up prints.
- Doubling the print width halves the DPI.
- Lower DPI can still look fine at a distance.
- Resampling cannot add real detail.
Common mistakes & gotchas
- Using the diagonal instead of an edge.
- Mixing centimetres and inches.
- Assuming screen PPI and printer DPI are the same.
- Upscaling a small image and expecting sharpness.
- Measuring the wrong edge.
Worked example
Worked example — 3,000 pixels across 10 inches
- DPI = 3,000 ÷ 10 = 300.
- Print width at 300 DPI = 3,000 ÷ 300 = 10 inches.
- A 4,000-pixel edge at 300 DPI prints 4,000 ÷ 300 = 13.33 inches wide.
- Stretching the same 3,000 pixels to 20 inches gives 150 DPI.
Result: 3,000 pixels over 10 inches is 300 DPI.
To load the form's own demo values, tap Try example above the Calculate button.
How to calculate / formula
DPI/PPI = pixels / inches.
Frequently asked questions
What is the difference between DPI and PPI?
PPI is pixels per inch of an image or screen; DPI is printer dots per inch.
What DPI do I need for printing?
Around 300 for close-up photos; less for large prints viewed from afar.
Can I increase DPI by resizing?
You can change the number but not add real detail.
How do I find the DPI of a screen?
Divide its pixel width by its physical width in inches.
Does the tool handle centimetres?
Enter inches; convert centimetres by dividing by 2.54.
Why does my print look soft?
The file may have too few pixels for the print size.