1. Hardware Calibration
Calibration Required
Web browsers often guess your resolution wrong. To get 100% precision, enter your native hardware resolution and screen diagonal below.
Calibrate once, and your browser remembers it forever.
×
Quick Fill:
✨ Detected System Details
Physical Res--
Logical CSS--
Pixel Scale (DPR)--
Color Depth--
Device OS--
Diagonal--
Measurement
0.00
cm
Live Measurement
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cm
Drag the red markers to measure
Saved Measurements
Export data locally to CSV
| Item | Type | Dimensions | Area | Perimeter | Date | ✕ |
|---|
Top Tricks & Strategies
📏 Measure Diagonals First: When calibrating a new monitor without specs, use a physical tape measure corner-to-corner on your screen glass. Enter that exact number in the Diagonal Inch box.
📐 Perfect for eCommerce: Shopping for glasses or jewelry? Lock your True Match scale, drag the product image onto the browser window, and use the 2D box to verify the physical fit.
⛶ The Fullscreen Blueprint: Press Fullscreen to turn your entire monitor into a 1:1 scale drafting board. The UI disappears, leaving only your measurements overlaying your screen.
Contact Support
Need help with calibration, have a feature request, or found a bug? Drop us an email directly, and we will get back to you as soon as possible.
onlinescreenruler@gmail.com
Send us an Email
Frequently Asked Questions
How accurate is the online screen ruler? +
When calibrated using the 'Hardware Calibration' or 'True Match' tools, the ruler achieves 100% 1:1 physical accuracy down to the sub-millimeter. It mathematically bypasses OS scaling to match your real-world dimensions.
Do I need to calibrate every time? +
No. Once locked, your device's exact scaling ratio is securely saved in your browser's local storage. It will remain perfectly accurate on future visits unless you clear your browser cookies.
How does the 'True Match' reverse calibration work? +
Manufacturers often round monitor sizes (e.g., 23.8" sold as 24"). True Match lets you align the digital ruler with a physical ruler on your desk. The software then reverse-engineers your exact physical pixel density (PPI) for flawless accuracy.
Can I measure custom shapes or polygons? +
Yes! Select "Custom Shape" from the mode dropdown. Click on the stage to drop vertex points around any object. The tool will automatically calculate the square area and physical perimeter.
Are my measurements saved privately? +
Absolutely. We have a strict zero-server-upload policy. Every measurement you take and save is stored entirely locally on your machine's hard drive using HTML5 LocalStorage.
How do I export my measurements? +
In the Saved Measurements section, click the "Download CSV" button. Your browser will instantly generate and download an Excel-compatible spreadsheet of all your logged data.