About Nosus Utilities
Free, browser-based tools for math, science, development, and everyday use — no download, no sign-up.
What it is
Nosus Utilities is a growing collection of free browser-based tools. The flagship tool — Online Ruler — renders at actual physical size on your screen. Unlike a generic screen ruler that just counts pixels, it calibrates to your display's true pixel density so measurements in centimeters, millimeters, and inches reflect real-world dimensions.
It works entirely in your browser — there's nothing to install, no account required, and no data is sent anywhere.
Why we built it
Most "online rulers" online are images at a fixed pixel width — they're only accurate on one specific monitor at 100% zoom. We wanted something better: a ruler that knows your screen's actual PPI and renders at true physical scale on any device.
The result is a tool you can actually trust for real measurements, whether you're checking a design mock-up, verifying a print crop, or measuring something you photographed on screen.
Key features
Three calibration methods
Auto-detect, screen diagonal input, or physical credit card alignment — get an accurate PPI reading on any device.
Five measurement units
cm, mm, inches, points, and pixels — switch instantly without losing your place.
Guide lines & markers
Drag guide lines from any ruler edge and drop point markers with exact x/y coordinates.
Device presets
One-click calibration for 12 common devices including MacBook, iPhone, iPad, and popular monitors.
Dark mode
Toggle between light and dark themes for comfortable use in any lighting condition.
Unit converter
Convert between mm, cm, inches, and px simultaneously without leaving the tool.
Completely free
This tool is and will always be free to use. No premium tier, no ads in the ruler workspace, and no paywall for calibration features. If you find it useful, sharing it with someone who needs to measure things on screen is all we ask.