Convert between coulomb/kilogram (C/kg), roentgen (R), millicoulomb/kilogram (mC/kg), microcoulomb/kilogram (µC/kg), tissue roentgen, parker, and rep — including C/kg to roentgen, roentgen to C/kg, mC/kg to roentgen, µC/kg to roentgen, roentgen to parker, roentgen to rep, and more.
This page covers every possible radiation exposure unit conversion between the 7 units in the converter above: coulomb/kilogram (C/kg), millicoulomb/kilogram (mC/kg), microcoulomb/kilogram (µC/kg), roentgen (R), tissue roentgen, parker, and rep. Each card below gives exact formulas for both directions.
Coulomb per kilogram to roentgen: multiply C/kg by 3,875.97. For roentgen to coulomb per kilogram (roentgen to C/kg): multiply R by 2.58 × 10⁻⁴. These are the two most common radiation exposure unit conversions in dosimetry.
1 C/kg = 3,875.97 R | 1 R = 2.58×10⁻⁴ C/kg
Millicoulomb per kilogram to roentgen (mC/kg to roentgen): multiply mC/kg by 3.87597. Roentgen to mC/kg (roentgen to millicoulomb/kilogram): multiply R by 0.258. The mC/kg to roentgen conversion is widely used in radiography instrument calibration.
1 mC/kg = 3.87597 R | 1 R = 0.258 mC/kg
Microcoulomb per kilogram to roentgen (µC/kg to roentgen): multiply µC/kg by 0.00387597. Roentgen to µC/kg (roentgen to microcoulomb/kilogram): multiply R by 258. The µC/kg to roentgen direction is common in environmental low-level exposure measurements.
1 µC/kg = 0.003876 R | 1 R = 258 µC/kg
Coulomb/kg to millicoulomb/kg (C/kg to mC/kg): multiply by 1,000. Millicoulomb/kg to coulomb/kg (mC/kg to C/kg): divide by 1,000. These SI prefix conversions are exact and frequently needed when comparing instrument readings in different scales.
1 C/kg = 1,000 mC/kg | 1 mC/kg = 0.001 C/kg
Coulomb/kg to microcoulomb/kg (C/kg to µC/kg): multiply by 1,000,000. Microcoulomb/kg to coulomb/kg (µC/kg to C/kg): divide by 1,000,000. The C/kg to µC/kg conversion is used when expressing very low radiation exposure levels precisely.
1 C/kg = 1,000,000 µC/kg | 1 µC/kg = 10⁻⁶ C/kg
Millicoulomb/kg to microcoulomb/kg (mC/kg to µC/kg): multiply by 1,000. Microcoulomb/kg to millicoulomb/kg (µC/kg to mC/kg): divide by 1,000. Useful when converting between survey meter scales in health physics.
1 mC/kg = 1,000 µC/kg | 1 µC/kg = 0.001 mC/kg
Roentgen to tissue roentgen: the conversion factor is numerically 1 (both use the same base unit value in this converter). The tissue roentgen to roentgen relationship reflects ionization in biological tissue versus air. Used in medical radiography and radiation oncology.
1 R ≈ 1 tissue roentgen (same factor)
Roentgen to parker: the parker is numerically equivalent to the roentgen, so 1 roentgen = 1 parker. Parker to roentgen is therefore a 1:1 conversion. The parker was introduced as an alternative name for the roentgen in certain historical radiotherapy contexts.
1 R = 1 parker | 1 parker = 1 R
Roentgen to rep: the rep (roentgen equivalent physical) shares the same conversion factor as the roentgen in this system, so 1 R ≈ 1 rep. Rep to roentgen is also approximately 1:1. The rep was historically used to relate air exposure to tissue dose before the gray was adopted.
1 R ≈ 1 rep | 1 rep ≈ 1 R
C/kg to tissue roentgen: multiply C/kg by 3,875.97 (same factor as C/kg to roentgen). Tissue roentgen to C/kg: multiply by 2.58 × 10⁻⁴. The tissue roentgen was designed for dosimetry in biological tissue, making this conversion relevant in medical physics.
1 C/kg = 3,875.97 tissue R | 1 tissue R = 2.58×10⁻⁴ C/kg
C/kg to parker: multiply C/kg by 3,875.97. Parker to C/kg: multiply parker value by 2.58 × 10⁻⁴. Since the parker equals 1 roentgen, the C/kg to parker conversion is identical to the C/kg to roentgen conversion.
1 C/kg = 3,875.97 parker | 1 parker = 2.58×10⁻⁴ C/kg
C/kg to rep: multiply C/kg by 3,875.97. Rep to C/kg: multiply rep value by 2.58 × 10⁻⁴. The rep shares its conversion factor with the roentgen, making C/kg to rep calculations straightforward.
1 C/kg = 3,875.97 rep | 1 rep = 2.58×10⁻⁴ C/kg
mC/kg to tissue roentgen: multiply mC/kg by 3.87597. Tissue roentgen to mC/kg: multiply by 0.258. These conversions apply the same factor as mC/kg to roentgen, since tissue roentgen and roentgen share the same conversion base.
1 mC/kg = 3.876 tissue R | 1 tissue R = 0.258 mC/kg
mC/kg to parker: multiply mC/kg by 3.87597. Parker to mC/kg: multiply by 0.258. The mC/kg to parker and parker to mC/kg conversions are used in legacy radiotherapy equipment calibration.
1 mC/kg = 3.876 parker | 1 parker = 0.258 mC/kg
mC/kg to rep: multiply mC/kg by 3.87597. Rep to mC/kg: multiply by 0.258. The rep was primarily a tissue dose unit, making the mC/kg to rep conversion relevant in historical dosimetry archives.
1 mC/kg = 3.876 rep | 1 rep = 0.258 mC/kg
µC/kg to tissue roentgen: multiply µC/kg by 0.00387597. Tissue roentgen to µC/kg: multiply by 258. Microcoulomb/kg to tissue roentgen is common in environmental radiation survey work where small exposures must be precisely expressed.
1 µC/kg = 0.003876 tissue R | 1 tissue R = 258 µC/kg
µC/kg to parker: multiply µC/kg by 0.00387597. Parker to µC/kg: multiply by 258. The µC/kg to parker conversion is encountered when referencing older industrial radiography standards that specified exposure limits in parker units.
1 µC/kg = 0.003876 parker | 1 parker = 258 µC/kg
µC/kg to rep: multiply µC/kg by 0.00387597. Rep to µC/kg: multiply by 258. The µC/kg to rep conversion appears in legacy health physics literature where the rep was used alongside roentgen measurements.
1 µC/kg = 0.003876 rep | 1 rep = 258 µC/kg
Parker to rep: both units share the same conversion factor as the roentgen, so 1 parker = 1 rep and 1 rep = 1 parker. All three — roentgen, parker, and rep — are legacy ionizing radiation exposure units with equivalent numerical values in this converter.
1 parker = 1 rep | 1 rep = 1 parker
Tissue roentgen to parker: 1 tissue roentgen = 1 parker (same base factor). Parker to tissue roentgen: 1 parker = 1 tissue roentgen. Both units measure ionizing radiation exposure and are numerically equivalent in this converter's reference frame.
1 tissue R = 1 parker | 1 parker = 1 tissue R
Tissue roentgen to rep: 1 tissue roentgen ≈ 1 rep (same factor). Rep to tissue roentgen: 1 rep ≈ 1 tissue roentgen. The rep (roentgen equivalent physical) was historically defined to approximate tissue dose from an exposure of 1 roentgen.
1 tissue R ≈ 1 rep | 1 rep ≈ 1 tissue R
All pairwise conversions between the 7 radiation exposure units supported by this converter.
| From | To | Multiply By | Example |
|---|---|---|---|
| C/kg | Roentgen (R) | 3,875.97 | 1 C/kg = 3,875.97 R |
| Roentgen (R) | C/kg | 2.58 × 10⁻⁴ | 1 R = 0.000258 C/kg |
| C/kg | mC/kg | 1,000 | 1 C/kg = 1,000 mC/kg |
| mC/kg | C/kg | 0.001 | 1 mC/kg = 0.001 C/kg |
| C/kg | µC/kg | 1,000,000 | 1 C/kg = 10⁶ µC/kg |
| µC/kg | C/kg | 10⁻⁶ | 1 µC/kg = 10⁻⁶ C/kg |
| mC/kg | Roentgen (R) | 3.87597 | 1 mC/kg = 3.876 R |
| Roentgen (R) | mC/kg | 0.258 | 1 R = 0.258 mC/kg |
| µC/kg | Roentgen (R) | 0.00387597 | 1 µC/kg = 0.003876 R |
| Roentgen (R) | µC/kg | 258 | 1 R = 258 µC/kg |
| mC/kg | µC/kg | 1,000 | 1 mC/kg = 1,000 µC/kg |
| µC/kg | mC/kg | 0.001 | 1 µC/kg = 0.001 mC/kg |
| Roentgen | Tissue Roentgen | 1 | 1 R = 1 tissue R |
| Roentgen | Parker | 1 | 1 R = 1 parker |
| Roentgen | Rep | ≈ 1 | 1 R ≈ 1 rep |
| Parker | Rep | 1 | 1 parker = 1 rep |
| C/kg | Tissue Roentgen | 3,875.97 | 1 C/kg = 3,875.97 tissue R |
| C/kg | Parker | 3,875.97 | 1 C/kg = 3,875.97 parker |
| C/kg | Rep | 3,875.97 | 1 C/kg = 3,875.97 rep |
| mC/kg | Tissue Roentgen | 3.87597 | 1 mC/kg = 3.876 tissue R |
| mC/kg | Parker | 3.87597 | 1 mC/kg = 3.876 parker |
| mC/kg | Rep | 3.87597 | 1 mC/kg = 3.876 rep |
| µC/kg | Tissue Roentgen | 0.00387597 | 1 µC/kg = 0.003876 tissue R |
| µC/kg | Parker | 0.00387597 | 1 µC/kg = 0.003876 parker |
| µC/kg | Rep | 0.00387597 | 1 µC/kg = 0.003876 rep |
The SI unit of ionizing radiation exposure. Measures the electric charge produced by radiation per unit mass of air. 1 C/kg = 3,875.97 R. Used in scientific calibration and when converting coulomb/kg to roentgen for legacy system compatibility.
One-thousandth of C/kg. 1 mC/kg = 3.876 R and 1 R = 0.258 mC/kg. The mC/kg to roentgen and roentgen to mC/kg conversions are standard in radiography instrument calibration sheets.
One-millionth of C/kg. 1 µC/kg = 0.003876 R and 1 R = 258 µC/kg. The µC/kg to roentgen conversion is essential in environmental radiation monitoring where exposure levels are very small.
The traditional unit of radiation exposure. 1 R = 2.58 × 10⁻⁴ C/kg. Named after Wilhelm Röntgen, discoverer of X-rays. Roentgen to coulomb per kilogram (roentgen to C/kg) and C/kg to roentgen conversions are the most frequently needed in medical physics.
A variant of the roentgen used in medical radiography, measured in biological tissue rather than air. Roentgen to tissue roentgen is numerically 1:1 in this converter. Used historically in radiation oncology and diagnostic radiology.
A legacy exposure unit equivalent to the roentgen. Parker to roentgen and roentgen to parker are 1:1 conversions. Found in older European and UK industrial radiography specifications and some historical radiation protection standards.
A historical unit predating the rad and gray. Rep to roentgen is approximately 1:1. The rep was defined as the absorbed dose in tissue from 1 roentgen of X-ray exposure. Now replaced by the gray (Gy) for absorbed dose measurements.
To convert C/kg to roentgen, multiply by 3,875.97. For example, 0.001 C/kg × 3,875.97 = 3.876 R. This coulomb per kilogram to roentgen conversion is the standard reference used in medical physics and dosimetry calibration. The coulomb/kg to roentgen factor comes from the exact definition: 1 R = 2.58 × 10⁻⁴ C/kg.
To convert roentgen to C/kg, multiply by 2.58 × 10⁻⁴. For example, 100 R × 2.58 × 10⁻⁴ = 0.0258 C/kg. The roentgen to coulomb per kilogram formula is exact: C/kg = R × 2.58 × 10⁻⁴. Use the converter above for instant roentgen to C/kg results.
mC/kg to roentgen: multiply by 3.87597. For example, 1 mC/kg = 3.876 R. Roentgen to mC/kg: multiply by 0.258. For example, 1 R = 0.258 mC/kg. The millicoulomb/kilogram to roentgen and roentgen to millicoulomb/kilogram conversions are commonly used in X-ray equipment calibration certificates.
µC/kg to roentgen: multiply by 0.00387597. For example, 100 µC/kg = 0.3876 R. Roentgen to µC/kg: multiply by 258. For example, 1 R = 258 µC/kg. The microcoulomb per kilogram to roentgen conversion is used in environmental radiation surveys where exposure levels are very low.
C/kg to mC/kg: multiply by 1,000. mC/kg to C/kg: divide by 1,000. These are SI prefix conversions: 1 C/kg = 1,000 mC/kg. The coulomb/kg to millicoulomb/kg and reverse are exact, with no rounding required.
C/kg to µC/kg: multiply by 1,000,000. µC/kg to C/kg: multiply by 10⁻⁶. For example, 0.001 C/kg = 1,000 µC/kg. The microcoulomb/kg to coulomb/kg conversion is exact.
Roentgen to parker: 1 roentgen = 1 parker (numerically equivalent). Parker to roentgen: 1 parker = 1 roentgen. The parker is simply an alternative name for the roentgen used in some historical European radiation standards. The roentgen to parker conversion never changes the numeric value.
Roentgen to rep: approximately 1:1 (same conversion factor). Rep to roentgen: also approximately 1:1. The rep (roentgen equivalent physical) was a precursor to the rad unit, defined as the absorbed dose in tissue equivalent to 1 R of X-ray exposure. In this converter, roentgen to rep uses the same factor as roentgen to tissue roentgen.
All three — tissue roentgen, parker, and rep — are legacy ionizing radiation exposure units with the same conversion base as the roentgen in this converter. Tissue roentgen to parker: 1:1. Parker to rep: 1:1. Tissue roentgen to rep: approximately 1:1. They are interchangeable for practical unit conversion purposes, though they originated from different measurement contexts in the history of radiation dosimetry.