CPM to Roentgen (R/h) Calculator
Convert CPM (counts per minute) to roentgen per hour (R/h) using your detector’s calibration factor. Includes unit-safe factor input, sensitivity ranges, copyable summary, and optional AI insights.
Important: There is no universal CPM ↔ R/h constant. You must use a calibration factor for your specific detector/setup. Factor direction and unit scaling matter.
Quick presets
Factor = CPM per R/h for your detector/setup. If your source is per mR/h or per µR/h, select that unit and the tool will normalize to CPM per R/h.
Factor presets (examples)
Enter a percent between 0 and 99.99. This does not change the core formula—only the range display.
Mode
CPM → R/h
CPM
350
Factor
1,000 CPM per R/h
R/h
0.35
Factor sensitivity
If your factor is uncertain, use an ±% range to see how the result changes.
Factor range: 800 - 1,200 CPM per R/h
Result range: 0.291667 - 0.4375 R/h
| Scenario | Factor (CPM per R/h) | Result (R/h) |
|---|---|---|
| -20% | 800 | 0.4375 |
| Base | 1,000 | 0.35 |
| +20% | 1,200 | 0.291667 |
Formula
R/h = CPM / factor
Assumptions
This is an estimate using your factor (CPM per R/h). The factor is detector- and context-specific (energy response, geometry, distance, shielding, settings). Do not treat this as a safety decision. CPM here means radiation counts per minute, not marketing CPM. R/h is an exposure-rate unit (roentgen per hour).
Copyable summary
Get practical interpretation, assumptions, and next steps based on your inputs (AI does not change the formula).
Avoid sharing personal or sensitive data. AI output is advisory and may be inaccurate.
Helpful notes on calibration factors and CPM ↔ R/h conversions:
- HHS REMM: roentgen definition and conversion factors
- dynode.nl: why CPM ↔ Sv/R is not universally valid
- SciHobby: why Geiger CPM readings differ between devices
- IoT Devices: SBM-20 factor derivation example (Cs-137)
- SE Inspector manual: example factor and conversion note
- Inayam: fixed R ↔ CPS conversion page (example, caution)
Explore other quick radiation/unit calculators on MDZ.ai.
What you get
Two-way conversion
Convert CPM → R/h or R/h → CPM with the same factor definition.
Unit-safe factor input
Enter Factor as CPM per R/h, or select CPM per mR/h / µR/h and we normalize automatically.
Sensitivity ranges
See how ±% uncertainty in your factor changes the result range.
Copy + AI insights
Copy a clean summary, and optionally ask AI for assumptions and next steps (AI never changes the formula).
How it works
Choose a direction
Pick CPM → R/h or R/h → CPM.
Enter your value
Input CPM or R/h.
Provide your factor
Use Factor = CPM per R/h (or choose mR/h / µR/h).
Review and copy
Review results, sensitivity range, and copy a summary.
FAQ
Need a quick CPM ↔ R/h estimate?
Use your detector’s calibration factor to convert instantly—then copy a summary to share.
Open the calculatorDisclaimer: This calculator provides an estimate based on your factor. It does not replace calibration or radiation safety procedures, and it does not provide medical/safety-critical advice.