AccuRuler by Michele

AccuRuler recreates and improves on the classic page ruler. Click the toolbar button, then click-drag anywhere to draw a measuring box with live width, height, start and end labels.

What makes it different:

• Auto-contrast chrome — the border, crosshair and labels flip black or white to match the background under your pointer, so the ruler never disappears on a dark site.
• Smart label placement — labels sit outside the box you're measuring and flip sides when there's no room, so they never cover the element you care about.
• No popups, no ads — a single-purpose tool that gets out of your way.

Tune it to your workflow:

• Colors: line/crosshair color, fill color and opacity, label background.
• Units: CSS pixels, physical pixels (× devicePixelRatio), millimetres or centimetres.
• Keyboard: Esc cancels or clears; arrow keys nudge 1px (Shift = 10px).

Private by design: AccuRuler collects nothing and makes no network requests.
Settings stay in your browser.