Unit:
0
centimeters
CM: 0
Inches: 0
MM: 0
Pixels: 0
Measure lengths in centimeters, inches, millimeters, or pixels directly on your screen.
This free online ruler lets you measure objects and distances directly on your screen in multiple units. Whether you need centimeters, inches, millimeters, or pixels, the ruler provides accurate measurements that you can calibrate to match your specific display. Perfect for quick measurements when you don't have a physical ruler handy.
Simply drag the blue handles on either end of the ruler to measure any distance. The measurement updates in real-time as you drag. Choose your preferred unit (CM, Inches, MM, or Pixels) using the buttons above the ruler. All unit conversions are shown simultaneously in the info panel below the ruler.
For the most accurate measurements, calibrate the ruler to your screen. Click the Calibrate button and use a credit card (standard 85.6mm width) or any object of known size as a reference. This adjusts the ruler to account for your screen's actual pixel density, ensuring measurements match real-world dimensions.
Click the Rotate button to switch between horizontal and vertical ruler orientations. This allows you to measure objects in any direction without needing to rotate your screen or the object being measured.
Use the Lock button to freeze the current measurement, preventing accidental changes while you record or reference the value. The Copy button instantly copies the measurement to your clipboard in your selected unit format, ready to paste into documents, spreadsheets, or design software.
Screen pixel density (DPI - dots per inch) varies between monitors. A standard assumption of 96 DPI is used by default, but actual values can range from 72 DPI on older monitors to over 200 DPI on high-resolution displays. Calibration compensates for this variation, giving you precise physical measurements regardless of your screen type.
The info panel shows your measurement in all four units simultaneously (CM, Inches, MM, and Pixels), making it easy to convert between units without any calculations. This is especially useful when working with designs that mix metric and imperial measurements.
The ruler works seamlessly on touch devices. On tablets and smartphones, simply touch and drag the handles to take measurements. The interface is optimized for touch with larger tap targets for comfortable use on any device.
Use this digital ruler for measuring photos and images on screen, checking dimensions before printing, verifying product sizes in online shopping, educational purposes in geometry and math, quick measurements for crafts and DIY projects, or any situation where you need to measure something displayed on your screen.