Convert roentgen to coulomb per kilogram instantly. Type in either field — results update live.
Selected R values converted to C/kg using the exact factor from this tool.
| R | C/kg |
|---|---|
| 0.01 | 0.00000258 |
| 0.1 | 0.0000258 |
| 1 | 0.000258 |
| 2 | 0.000516 |
| 3 | 0.000774 |
| 5 | 0.00129 |
| 10 | 0.00258 |
| 20 | 0.00516 |
| 50 | 0.0129 |
| 100 | 0.0258 |
| 1,000 | 0.258 |
Exact conversion factors in both directions, plus a worked example.
1 R = 0.000258 C/kg
1 C/kg = 3875.9689922481 R
To convert roentgen to coulomb per kilogram, multiply by 0.000258.
To convert coulomb per kilogram to roentgen, multiply by 3875.9689922481.
Example: convert 10 R to C/kg
10 × 0.000258 = 0.00258 C/kg
Short background on the units used in this conversion.
The roentgen (R) equals 0.000258 coulomb per kilogram — the classic unit of photon exposure in air for X-rays and gamma rays.
Roentgens label X-ray tube output, radiographic technique factors, and legacy exposure specifications — the most searched exposure conversion.
Coulomb per kilogram (C/kg) is the SI unit of exposure — ionization charge produced per unit mass of air.
C/kg is the modern SI replacement for the roentgen in radiation exposure metrology.
C/kg = R × 0.000258R = C/kg × 3,875.9689922481, using the same exact factors as this converter.