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Precision Ruler Suite
Use calibrated on-screen measurement and switch to printable rulers when physical verification is required.
Screen Calibration
Calibrate once and measure directly on screen in centimeters and inches.
Printable Assets
Online Actual Size Ruler
A precise, calibrated ruler on your screen. Use a credit card to calibrate your display for accurate on-screen measurements, then double-check critical dimensions with a physical ruler.
Waiting for calibration...
How to use this online ruler
Most screens have different pixel densities (PPI), which means "100 pixels" looks different on a phone versus a desktop monitor. To make this ruler accurate, we need to calibrate it.
- Click "Calibrate" if the modal doesn't appear automatically.
- Grab a standard credit card (or any card from your wallet).
- Adjust the slider until the blue box on the screen matches the physical card width exactly.
- Click "I'm Calibrated".