# Online-Ruler.Onl

Canonical site: https://www.online-ruler.onl/

Online-Ruler.Onl is a free browser-based screen ruler. The initial scale is an estimate. Users must calibrate the current display with a standard 85.60 mm ID-1 bank card or a manufacturer-listed display diagonal before relying on physical-size readings. Browser zoom should remain at 100%. Critical measurements require a suitable certified physical instrument.

## Primary pages

- Screen ruler and calibration: https://www.online-ruler.onl/
- Printable ruler with 100 mm scale check: https://www.online-ruler.onl/print-ruler
- Measurement guides: https://www.online-ruler.onl/blog
- Measurement and editorial methodology: https://www.online-ruler.onl/about
- Privacy policy: https://www.online-ruler.onl/privacy
- Measurement limitations: https://www.online-ruler.onl/disclaimer

## Core guides

- How to read a ruler: https://www.online-ruler.onl/blog/how-to-read-a-ruler
- How to use a ruler: https://www.online-ruler.onl/blog/how-to-use-a-ruler
- How to measure on a phone: https://www.online-ruler.onl/blog/how-to-measure-on-phone
- Metric vs U.S. customary measurement: https://www.online-ruler.onl/blog/metric-vs-imperial
- Measurement units guide: https://www.online-ruler.onl/blog/measurement-units-guide

## Editorial notes

Measurement content is maintained by the Online Ruler Editorial Team. Standards-based unit definitions prioritize primary sources from NIST and BIPM. Corrections can be submitted through https://www.online-ruler.onl/contact.