Convert Roentgens to Coulombs per kilogram
Convert Roentgens (R) to Coulombs per kilogram (C/kg) instantly and accurately.
Conversion Formula
C/kg = R × 0.000258
About Roentgens
The roentgen (R) equals exactly 2.58 × 10⁻⁴ C/kg, the historical unit of X-ray and gamma-ray exposure defined in 1928 (ICRU) and redefined exactly in 1962. Still widely used in the US: field survey instruments read in R/h; NRC and EPA regulations cite R and mR; the Chernobyl accounts famously reported readings in R/h. 1 R = 2.58 × 10⁻⁴ C/kg.
About Coulombs per kilogram
The coulomb per kilogram (C/kg) is the SI derived unit of radiation exposure, equal to 1 coulomb of ion charge liberated per kilogram of dry air. It replaced the roentgen in SI. Calibration of clinical X-ray beams with free-air ionisation chambers and parallel-plate chambers yields results in C/kg. 1 C/kg ≈ 3876 R.
Quick Reference Table
| Roentgens (R) | Coulombs per kilogram (C/kg) |
|---|---|
| 1 R | 0.000258 C/kg |
| 2 R | 0.000516 C/kg |
| 5 R | 0.00129 C/kg |
| 10 R | 0.00258 C/kg |
| 25 R | 0.00645 C/kg |
| 50 R | 0.0129 C/kg |
| 100 R | 0.0258 C/kg |