PPI Calculator

How to Use This PPI Calculator

Retail listings love the words “Full HD” and “4K” but bury the diagonal inch measurement three scrolls down. Two panels can share the same pixel grid yet feel nothing alike when one stretches that grid across a bigger piece of glass. In my experience spec-checking gear before purchase orders, teams waste hours debating resolution labels while the sharper question sits untouched: how many pixels land in each physical inch?

Think of PPI like thread count on bedsheets. Same blanket size with more threads feels tighter and smoother. Resolution tells you the total thread count; diagonal inches tell you the blanket width; PPI tells you how dense the weave feels when you sit at normal viewing distance. This page runs that density math from three inputs you already have on the box or in OS display settings.

• Start on Single display. Type pixel width and pixel height (from Windows Display settings, macOS System Settings, or the product datasheet).
• Enter diagonal size in inches or centimeters exactly as the manufacturer prints it near the model name.
• Read PPI in the Result line, then review the Display metrics table for PPI², diagonal pixels, dot pitch, megapixels, and aspect ratio.
• Metric packaging. Switch the diagonal unit to centimeters when the spec sheet is EU-format; PPcm appears in the table when cm is selected.
• Compare two screens when you are down to two monitors with different diagonals and resolutions. The Compare metrics table lists both side by side; the Result line shows PPI for each plus the density gap.

All math runs locally in your browser. Inventory or unreleased product specs stay on your machine unless you copy them out yourself.

PPI Calculator Formulas and Practical Applications

Standard LCD, OLED, and IPS panels assume square pixels. Ultra-wide or legacy panels with rectangular subpixels may deviate slightly; treat output as a planning number, not a lab certification. The workflow below matches how display engineers quote density on cut sheets.

Step one: diagonal in pixels

diagonal_px = √(width_px² + height_px²)

Width and height are orthogonal legs of a right triangle; the diagonal pixel count is the hypotenuse. For 1920 × 1080, that hypotenuse is about 2202.91 px. Skipping this step and dividing width by inches alone is a common mistake—it ignores panel height and misstates density.

Step two: pixels per inch

PPI = diagonal_px ÷ diagonal_in

Convert centimeter diagonals first: diagonal_in = diagonal_cm ÷ 2.54. A compact tablet with a short diagonal can exceed 300 PPI while a wall-mounted TV sits below 100 PPI and still looks fine from the couch.

PPcm, PPI², and dot pitch

PPcm = diagonal_px ÷ diagonal_cm

PPI² = PPI × PPI

dot pitch (mm) = (diagonal_in ÷ diagonal_px) × 25.4

PPI² describes pixels packed into a one-inch square region of the panel. Dot pitch is the hardware center-to-center spacing—useful when datasheets quote millimeters instead of PPI. Moving onto procurement, higher PPI generally means cleaner spreadsheet text and UI chrome at arm’s length.

Megapixels, aspect ratio, and related tools

Total pixel count is width × height; divide by one million for megapixels. Aspect ratio simplifies by greatest common divisor (1920:1080 → 16:9). Shape alone lives in the Aspect Ratio Calculator. Print width from pixels at a fixed DPI belongs in the Pixels to Inches Converter. Capture on-screen references with the Online Screenshot tool, then read pixel dimensions back into this calculator.

Standard Units and Conversion Tables

Use these ballparks when sanity-checking vendor PDFs. Always combine resolution with diagonal—never compare PPI using resolution alone.

• 1920 × 1080, 24 in diagonal: about 92 PPI (typical office monitor).
• 2560 × 1440, 27 in: about 109 PPI (common QHD desk display).
• 3840 × 2160, 27 in: about 163 PPI (4K at close range).
• 1920 × 1080, 10 in: about 220 PPI (dense portable panel class).
• Length: 1 in = 25.4 mm; 1 in = 2.54 cm (exact definitions).
• PPcm to PPI: PPI = PPcm × 2.54.

Frequently Asked Questions