Online Ruler
Calibrate your screen with a credit card and measure objects in centimeters or inches with pixel-perfect tick marks. No download, works in your browser.
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What is Online Ruler?
The Online Ruler turns your screen into a calibrated measuring tool. After a quick PPI calibration using a credit card or any known-length reference, you can measure objects in centimeters or inches with pixel-accurate tick marks - all rendered locally in your browser.
Key Benefits
- Measures in centimeters or inches with calibrated accuracy
- PPI calibration ensures correct physical dimensions per screen
- Shows screen width and height in your chosen unit
- No app, no download - just open the page and measure
Common Use Cases
- •Measuring small objects when no physical ruler is nearby
- •Checking screen dimensions for design and layout work
- •Verifying print sizes before sending to a printer
- •Quick measurement of jewelry, components, or paper sizes
- •Educational demonstrations of unit conversion and PPI
Use the Online Ruler
- Calibrate with a credit card: Place a credit card (85.60 mm long) against the ruler and adjust the PPI value until the marks match the card edge.
- Choose your unit: Switch between centimeters and inches - the tick marks and labels update automatically.
- Measure your object: Place the object against the screen and read the measurement from the tick marks.
- Check screen dimensions: The screen width and height in calibrated units are shown below the ruler for reference.
Key Features
- Canvas-drawn tick marks at PPI-calibrated intervals
- Centimeter and inch units with 10/16 subdivision ticks
- PPI calibration input for accurate screen measurement
- Shows your screen width and height in calibrated units
- Reference card hint: use a credit card (85.60 mm) to verify
- No download, no app - runs in your browser