Quickly measure objects on your screen with a calibrated online ruler — works in any browser on desktop or phone.
1
Open the online ruler
Go to fourmeld.com/tools/ruler.
2
Calibrate to your screen
Enter your screen size or use a known object to calibrate the ruler.
3
Measure your object
Place the object against the screen and read the measurement in CM or inches.
4
Switch between units
Click CM or INCH to switch measurement units instantly.
Tips
- Bookmark this tool for quick access in the future
- Works on any device — desktop, tablet or mobile phone
- No signup or account needed — just open and use
FAQs
How accurate is an online ruler?
Very accurate once calibrated to your screen size. Without calibration, accuracy depends on your screen resolution.
Can I use this on a phone?
Yes — the online ruler works on phone screens too.
How do I calibrate the ruler?
Enter your screen size (diagonal in inches) in the calibration field, or align a credit card (85.6mm) with the ruler.
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