DPI (dots per inch) technically refers to printer dots — how many ink dots a printer places per inch of paper. PPI (pixels per inch) refers to screen pixels — how many display pixels fit in one inch. In everyday usage the terms are often used interchangeably, especially when talking about image resolution.

What DPI do I need for printing?

300 DPI is the standard for high-quality photo prints. 150–200 DPI is acceptable for large-format prints viewed from a distance (posters, banners). 72–96 DPI is typical for screen display. For newspaper printing, 150 DPI is common. For fine art giclée prints, 360–720 DPI may be used.

How do I calculate the DPI of my monitor?

To calculate your monitor's DPI: divide the horizontal pixel count by the screen width in inches. For example, a 1920×1080 monitor that is 24 inches wide (diagonal) has a diagonal of √(1920²+1080²) ≈ 2203 pixels. Divide 2203 by the 24-inch diagonal to get approximately 92 DPI.

A megapixel is one million pixels. A 12-megapixel camera captures images containing 12,000,000 pixels — typically arranged as a rectangle like 4000×3000. More megapixels means you can print larger at the same DPI or crop more aggressively without losing detail.

What pixel dimensions do I need for an A4 print at 300 DPI?

A4 paper is 8.27 × 11.69 inches. At 300 DPI you need 2480 × 3508 pixels. At 150 DPI you need 1240 × 1754 pixels. This calculator's resize mode will compute these dimensions automatically when you enter the target DPI and physical size.

DPI / PPI Calculator

Calculate screen DPI, print resolution, and resize pixels for a target DPI. 100% client-side.

Width (px)

Height (px)

Diagonal (inches)

Enter dimensions above to calculate DPI.

Common Print Size Reference (click to expand)

Format	Inches	px @ 72	px @ 150	px @ 300

How to Use the DPI / PPI Calculator

Screen DPI — enter your monitor's pixel resolution and diagonal screen size in inches to calculate exact PPI.
Print DPI — enter pixel dimensions and physical print size to see the resulting print resolution.
Resize for Target DPI — enter the desired physical size and target DPI to get the required pixel dimensions.
Megapixel — enter width and height in pixels to calculate total megapixels and aspect ratio.

DPI vs PPI: What's the Difference?

DPI (dots per inch) and PPI (pixels per inch) describe image resolution but in different contexts. PPI is used for digital displays — it tells you how densely pixels are packed in a screen. DPI is used for print — it tells you how many ink dots a printer places per linear inch. When you export an image for print, the DPI setting in the file metadata tells the printer or layout application how large to render it, though most modern software re-samples images to fit the specified size anyway.

What DPI Should You Use?

Screen / web — 72–96 PPI for standard displays; 144–192 PPI for Retina/HiDPI screens
Standard photo prints — 300 DPI for prints up to 8×10 inches
Large format posters — 100–150 DPI (viewed from further away)
Billboards — 10–25 DPI (viewed from tens of feet)
Fine art giclée prints — 360–720 DPI for maximum detail
Newspaper — 150–200 DPI

How DPI Affects File Size

Doubling the DPI quadruples the pixel count (and roughly quadruples the file size for uncompressed images). A 4×6 inch image at 300 DPI is 1200×1800 pixels = 2.16 megapixels. The same image at 600 DPI would be 2400×3600 pixels = 8.64 megapixels. For most print-on-demand services, 300 DPI is the sweet spot — higher resolutions rarely produce visible improvement and create unnecessarily large files.

Retina and High-DPI Displays

Apple's Retina displays pack approximately twice the pixels into the same physical space as standard displays, resulting in 220–600 PPI depending on the device. iOS uses a CSS pixel ratio of 2×–3×, meaning a CSS pixel maps to 4–9 physical pixels. When designing for web, use the CSS pixel (logical pixel) for layout; supply 2× and 3× image assets for sharp rendering on high-DPI screens. The viewport meta tag controls how the browser maps CSS pixels to physical pixels.

Megapixels and Print Quality

A higher megapixel count gives you more flexibility for large prints and heavy cropping. A 12 MP camera (4000×3000 px) can produce a 13.3×10 inch print at 300 DPI — comfortably photo-lab quality. A 24 MP camera (6000×4000 px) can print up to 20×13.3 inches at 300 DPI. For web-only use, anything above 2–3 MP is usually more than sufficient and just adds storage overhead. Use the megapixel mode in this calculator to see exactly what print sizes your current resolution supports at various DPI targets.

Frequently Asked Questions

DPI (dots per inch) refers to printer resolution — how many ink dots per inch. PPI (pixels per inch) refers to screen pixel density. In common usage the terms are interchangeable when discussing image resolution, though technically precise usage distinguishes them.

300 DPI is the gold standard for photo-quality prints. 150–200 DPI is fine for posters viewed from a distance. 72–96 DPI is standard for screen display. For newspaper print, 150 DPI is common; for fine art giclée prints, 360 DPI or higher may be used.

Calculate the diagonal pixel count: √(width² + height²). Then divide by the diagonal screen size in inches. For a 1920×1080 screen at 24 inches diagonal: √(1920²+1080²) ÷ 24 ≈ 92 PPI.

A megapixel is one million pixels. A 12 MP camera produces 12,000,000 pixels — typically a rectangle like 4000×3000. More megapixels enables larger prints at the same DPI and more aggressive cropping without visible quality loss.

A4 is 8.27×11.69 inches. At 300 DPI that requires 2480×3508 pixels. At 150 DPI you need 1240×1754 pixels. Use the "Resize for Target DPI" mode in this calculator to get exact dimensions for any paper size and DPI.