Settings
Ruler (cm)
Current DPI: 96 | 1 cm = 37.80 pixels
Reference Objects
US Quarter (24.26mm)
1 inch square
USB-A (12mm width)
Online Screen Ruler & Scale Tool
Measure objects on your screen with a real-world ruler. Free on-screen ruler tool for inches and centimeters. Calibrate to your display's DPI.
How It Works
The tool displays a ruler on your screen that you can calibrate to your monitor's actual DPI. Once calibrated, it provides accurate real-world measurements in inches and centimeters directly on your screen.
Common Use Cases
- Measuring the actual size of a design element on screen
- Checking dimensions when you don't have a physical ruler handy
- Calibrating your monitor for accurate on-screen measurements
- Verifying the size of printed elements before sending to a printer
Frequently Asked Questions
After calibration with a known reference (like a credit card), the ruler provides measurements accurate to within a few millimeters.
Hold a physical object of known size (like a credit card or a physical ruler) against the screen and adjust the calibration slider until they match.
Yes, it works on any monitor. Accuracy depends on proper calibration, which adjusts for your specific display's pixel density.
Monitors have different pixel densities (DPI). A 96 DPI monitor shows pixels larger than a 144 DPI Retina display. Calibration adjusts for your specific display.
Yes, the ruler displays both metric (centimeters, millimeters) and imperial (inches) measurements simultaneously.
Common references: a credit/debit card (85.6 × 53.98 mm), a US dollar bill (156 × 66.3 mm), or a standard sheet of paper (A4: 210 × 297 mm, Letter: 216 × 279 mm).
Yes, but accuracy depends on calibration. Mobile screens have high DPI, so calibration with a physical reference object is especially important.