Screen Ruler
Free online screen ruler. Measure anything on your screen in pixels, centimeters, or inches. Drag and resize — no install required.
How to Use the Screen Ruler
Choose Ruler mode for linear measurements or Box mode for 2D area measurements. Drag the ruler or box anywhere on the measurement area. Resize by dragging the handles on either end (Ruler) or the 8 edge/corner handles (Box). Toggle between pixels, centimeters, and inches using the unit buttons. If you need accurate physical measurements, use the DPI Calibrate button and align a standard credit card to the on-screen outline.
About This Tool
Measure anything on your screen with a draggable, resizable ruler or measurement box. Supports pixels, centimeters, and inches with DPI calibration for accurate physical measurements. No download or install required — runs entirely in your browser. Useful for designers, developers, and anyone who needs to measure UI elements, images, or screen distances. Pair with Image Resizer to resize images to specific pixel dimensions or Image Cropper to crop to exact sizes.
Quick Reference Table
| Shortcut | Action |
|---|---|
| R | Switch to Ruler mode |
| B | Switch to Box mode |
| U | Cycle unit (px → cm → in) |
| C | Copy measurement to clipboard |
| Arrow keys | Nudge ruler/box by 1 px |
| Shift + Arrow | Nudge by 10 px |
Frequently Asked Questions
How accurate are the centimeter and inch measurements?
Accuracy depends on your screen's DPI. Use the Calibrate button with a standard credit card (85.6 mm wide) to set your screen's true DPI. Without calibration, the tool estimates DPI from your browser, which may be off by 5–15%.
Does this upload anything to a server?
No. The ruler runs entirely in your browser with pure JavaScript and the Canvas API. Nothing is sent to any server.
Can I measure elements on other websites?
The ruler measures within the tool's measurement area. To measure other websites, take a screenshot and compare dimensions, or use the pixel measurements as a reference.
Does it work on touchscreens?
Yes. Touch drag and pinch gestures are supported for positioning and resizing the ruler and measurement box.