Everything here is arithmetic plus reference data, offered as-is. What that does and doesn’t cover:

The math is exact; the physical world isn’t

This site computes ideal values — √(w²+h²)÷diagonal for density, pixels÷dpi for print size, gcd reduction for ratios. Real hardware adds variance the math can’t see:

• Advertised diagonals are nominal. A “27-inch” panel may measure 26.96″; a “6.1-inch” phone 6.06″. At the same resolution, actual PPI shifts a percent or two. Vendor PPI numbers are also frequently rounded down for marketing.
• Printers have their own limits. A file sized for 300 ppi can still print worse than expected: driver resampling, ink spread on uncoated stock, halftone screening and viewing conditions all sit between your file and the result. Ordering a paid print run? Proof a small section first — the pixels were right, but paper is where assumptions go to die.
• Panel scaling isn’t always integer. OS-level fractional scaling (125%, 150%) means a CSS pixel can span a non-integer number of physical ones; our CSS-pixels readout reports the browser’s numbers faithfully, but compositing smooths over the fraction differently per platform.

Reference data and presets

Device presets reflect published specifications as we understand them, and paper sizes follow their formal definitions (ISO in millimetres, US formats in inches, converted at 25.4 mm/in). Manufacturers revise panels mid-cycle and spec sheets lie politely; where our preset and your hardware disagree, trust the hardware — and tell us.

Not professional advice

Guides such as how much resolution print needs and PPI vs DPI explain conventions and arithmetic. They are not a substitute for your print shop’s file-prep specifications — a lab’s stated requirements always override generic guidance, ours included. Nothing here is engineering, procurement or legal advice.

Advertising

The site may show third-party ads (for instance Google AdSense) to offset hosting. Advertisers have zero influence on computed results or article content — the arithmetic doesn’t know an ad exists.

Liability

Use of this site is at your own risk. To the maximum extent permitted by law, PixelCalc and its maintainers accept no liability for losses connected with its use — including misprinted jobs, misordered materials and decisions made on nominal specifications. Verify consequential numbers against the actual device, lab or standard before committing.