Built to measure, not to distract

ruleronphone is an on-screen ruler you open in the browser. The home page is the tool: multi-edge rulers you can place on any side, a thin toolbar, and an empty canvas so physical objects stay visible.

We optimize for calibration quality and a quiet measuring surface - not for ads in the canvas. Units, calibration, theme, edges, and Hide Info preferences stay in localStorage on your device.

Calibrate with a credit/ID-1 card, A4 or Letter paper, a custom length, device helpers, or diagonal. Use Select for width, height, diagonal, and area; paired Guides for spacing; and a short tour when you are new.

The product aesthetic is restrained: near-black ink on a near-white canvas, hairline borders, and mono labels for technical chrome. Marketing copy lives under Hide Info and on dedicated pages so the ruler stays quiet when you need it.