Prism Constant Check Calculator
A free, browser-based calculator. Runs entirely in your browser — no sign up, nothing stored.
100% FreeRuns in your browserIntermediate
Enter Values
Enter your values and press Calculate to see results.
How to use this calculator
- Enter the measured distance.
- Enter the prism constant in millimetres (often −30).
- Press Calculate for the corrected distance.
How it works
Applies the prism (reflector) constant to an EDM measurement: corrected distance = measured distance + prism constant.
Worked example
150.000 m, −30 mm prism. Corrected distance = 149.970 m.
Frequently asked questions
What prism constant should I use?
It must match your reflector and instrument setting — common values are 0 mm and −30 mm. Check the prism's spec.
Related tools
Tip: Enter any known values to calculate the remaining results.
All calculations run in your browser. Your inputs are never saved or transmitted.