Example: Activity
Convert 1.2 mCi to MBq.
Result: —
Medical isotope typical activity for diagnostic imaging.
Radiation & Radiometry
Advanced Radiation Unit Converter
Convert ionizing radiation and radiometry quantities including Activity, Exposure, Absorbed Dose, Equivalent Dose, Dose Rate, Kerma, LET, Particle Flux, plus radiometric quantities like Radiant Flux, Radiant Energy, Radiant Intensity, Radiant Exposure, Energy Density and Power Density.
1 Ci = 3.7×10¹⁰ Bq
1 Bq = 60 dpm
1 rad = 0.01 Gy
1 rem = 0.01 Sv
1 R = 2.58×10⁻⁴ C/kg
1 Gy = 1 J/kg
SI first
Most categories use SI base units (Bq, C/kg, Gy, Sv, W, J, W/m², J/m³) then convert to legacy units when common.
Physics vs biology
Gray and kerma are physical energy-per-mass. Sievert is weighted for biological effect. This tool converts units only.
Some items are descriptive
A few topics like spectrum are not single "units." This page includes a practical placeholder category so you can label conversions or normalize related units.
Interactive Converter
Pick a category, choose units, enter a value, then copy the result. Use Swap to reverse units.
Category explanation
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Select a category to see what it means and where it is used.
Base unit: —
Plain language
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Common formula
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Real world uses
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Tip: You can type commas (like 10,000). The converter reads it as 10000.
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Enter a value to convert
Conversion Formula
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Notes: Some categories have physics context (geometry, spectra, biological weighting). This tool converts units and shows standard relationships, but does not model environments.
Understanding Radiation Units: Charts & Comparisons
Activity Unit Scale (Bq vs Ci)
Visual comparison of common activity conversions:
Absorbed Dose Scale (Gray vs Rad)
Relative magnitudes of common dose values:
Unit Conversion Reference Tables
Activity Conversions
| Becquerel (Bq) | Curie (Ci) | Disintegrations/min (dpm) | Common Use |
|---|---|---|---|
| 1 Bq | 2.7×10⁻¹¹ Ci | 60 dpm | Single decay per second |
| 1 kBq | 2.7×10⁻⁸ Ci | 60,000 dpm | Trace amounts |
| 1 MBq | 2.7×10⁻⁵ Ci | 60 million dpm | Medical isotopes |
| 1 GBq | 2.7×10⁻² Ci (0.027 Ci) | 60 billion dpm | Strong sources |
| 3.7×10¹⁰ Bq | 1 Ci | 2.22×10¹² dpm | Historical reference unit |
Absorbed Dose Conversions
| Gray (Gy) | Rad | Millirad (mrad) | Context |
|---|---|---|---|
| 0.01 Gy | 1 rad | 1,000 mrad | Legacy unit basis |
| 0.1 Gy | 10 rad | 10,000 mrad | Industrial sterilization |
| 1 Gy | 100 rad | 100,000 mrad | 1 joule per kilogram |
| 2.5 Gy | 250 rad | 250,000 mrad | High dose therapy |
| 5 Gy | 500 rad | 500,000 mrad | Lethal acute dose |
Equivalent Dose (Biological Effect)
| Sievert (Sv) | Millisievert (mSv) | Rem | Health Impact |
|---|---|---|---|
| 0.001 Sv | 1 mSv | 100 mrem | Annual background + CT scan |
| 0.01 Sv | 10 mSv | 1,000 mrem | Occupational limit (5-year average) |
| 0.05 Sv | 50 mSv | 5,000 mrem | Increased cancer risk threshold |
| 1 Sv | 1,000 mSv | 100 rem | Acute radiation sickness |
| 6 Sv | 6,000 mSv | 600 rem | Lethal dose (LD50/60) |
SI vs Legacy Units: Key Differences
Activity
SI: Becquerel (Bq) = 1 decay/s
Legacy: Curie (Ci) = 3.7×10¹⁰ Bq
Why: Ci was defined from radium-226 activity; Bq is simpler.
Absorbed Dose
SI: Gray (Gy) = 1 J/kg
Legacy: Rad = 0.01 Gy
Why: Rad predates SI; Gy is direct energy measurement.
Equivalent Dose
SI: Sievert (Sv) with weighting factors
Legacy: Rem = 0.01 Sv
Why: Both account for biological effect; Sv uses modern factors.
Exposure (Air)
SI: Coulomb/kg (C/kg) in air
Legacy: Roentgen (R) = 2.58×10⁻⁴ C/kg
Why: R was practical for ionization chambers; C/kg is fundamental.
Dose Rate
SI: Sv/s or Sv/h
Legacy: rem/h or mrem/h
Why: Time unit conversion follows dose unit conversion.
Power/Flux
SI: Watt (W) or W/m²
Legacy: erg/s or W/cm²
Why: W is SI standard; W/cm² is common in laser safety.
Key Physics Concepts
Gray (Gy) vs Sievert (Sv)
Gray measures physical absorbed dose (energy deposited per mass). Sievert adjusts this with weighting factors for radiation type (alpha, beta, neutron, etc.) and tissue sensitivity. Same absorbed dose of different radiation types produces different biological effects.
Kerma vs Absorbed Dose
KERMA (Kinetic Energy Released per unit Mass) is energy given to charged particles by photons. Absorbed Dose is energy actually deposited in material. For photons, kerma ≈ absorbed dose in small volumes, but differs in cavities or at interfaces.
Radiant Flux vs Radiant Intensity
Radiant Flux (Φ) is total power (W) emitted by a source in all directions. Radiant Intensity (I) is power per unit solid angle (W/sr), describing directional behavior. For an isotropic source: Φ = 4π × I.
Half-Life Applications
Half-life determines how long a source remains active. Short half-lives (hours to days) suit medical tracers; long half-lives (years to millennia) apply to waste storage and environmental contamination. Activity after time t: A(t) = A₀ × (1/2)^(t/T½).
Linear Energy Transfer (LET)
LET describes energy loss per unit track length (keV/µm). High-LET particles (alpha, heavy ions) cause dense ionization and greater biological damage per unit dose than low-LET particles (electrons, photons). This is why equivalent dose weighting factors differ.
Worked Examples
Pre computed examples help visitors learn magnitudes and verify conversions quickly.
Example: Absorbed Dose
Convert 250 rad to Gy.
Result: —
High dose used in radiation therapy and sterilization.
Example: Power Density
Convert 35 mW/cm² to W/m².
Result: —
Typical laser or UV lamp irradiance measurement.
Example: Dose Rate
Convert 2.5 mSv/h to µSv/h.
Result: —
Area monitoring and time-in-area safety planning.
Example: Half-Life
Convert 5.27 years to days (Co-60).
Result: —
Planning storage and decay calculations for sources.
Example: Radiant Flux
Convert 500 mW to W.
Result: —
Laser power and radiometric source characterization.
FAQ
What is the difference between gray (Gy) and sievert (Sv)?
Gy is absorbed dose (J/kg) – the physical energy deposited. Sv is weighted dose for biological effect. This page converts units only. Weighting factors depend on radiation type and tissue.
How do Bq and Ci convert?
1 Ci = 3.7×10¹⁰ Bq. Also 1 Bq = 60 dpm. Bq is decays per second (SI). Ci is a legacy unit still used in many industries.
What is radiant flux vs radiant intensity?
Radiant flux (W) is total radiant power. Radiant intensity (W/sr) is power per steradian. For isotropic emission: Flux = 4π × Intensity.
Why are there two dose units (Gy and Sv)?
Gray (Gy) measures physical energy deposited (same for all radiation types). Sievert (Sv) adjusts for biological effect using weighting factors for radiation type and tissue sensitivity. Protection standards use Sv; physics research often uses Gy.
What is LET and why does it matter?
Linear Energy Transfer (LET) is energy lost per unit track length (keV/µm). High-LET particles (alpha, heavy ions) cause denser ionization and greater biological damage than low-LET (electrons, photons) at the same absorbed dose.
How do I convert dose rate over different time periods?
Dose rate units include time: Sv/h, mSv/day, etc. Convert to base unit (Sv/s), then multiply by the new time period in seconds. Example: 5 mSv/h = 5×10⁻³ Sv / 3600 s ≈ 1.39 µSv/s.