Dose Rate to Radioactivity Calculator (with optional shielding)
Published: Apr 14, 2026
Source: Ionactive Radiation Protection Resource
Ionactive Dose Rate to Radioactivity Calculator
Version 1.1 - release 06 January 2026
Looking for another calculator - try Radioactivity to Dose Rate Calculator (with shielding and dose rate ratio options). If you are working with neutron sources then the following resource will be useful: Ionactive Neutron Dose Rate Calculator.
Dose Rate to Radioactivity
Formal advice
If you are after formal advice on calculating radioactivity based on dose rates or the shielding required then head over to our Radiation Protection Adviser (RPA) services , or try our online radiation protection training courses for in-depth study of gamma emissions from radioactive materials and shielding.
Release notes
Version 1:0. The Dose Rate to Radioactivity Calculator is fully working with a limited range of radionuclides - more to be added over the coming weeks. Each data set has been analysed using the latest version of MicroShield, and spot checked using Monte Carlo simulation via openMC. Buildup is included as standard in the calculation process, but is not equally applied across all gamma radionuclides. For example, buildup applied to medium energy (100-300 keV) gamma photons, in low density (and low Z number) materials such as water can significantly exaggerate shielding required (well beyond a sensible factor of safety) - and so suitable modifications have been made. No beta dose rate contribution is considered (this will feature in a separate calculator).
Version 1:1 (current version). Ra-226 (sealed source) has been added. Assuming a sealed source means that the decay series below Ra-226 (i.e. Rn-222 → Pb-206) will be in secular equilibrium with the parent (i.e. current activity of Ra-226) for aged sources (>> one month), which will be relevant for almost all likely sources. Therefore the photon contributions from Pb-214 / Bi-214 will be significant, which would not be the case for unsealed Ra-226 (e.g. a salt) where the Rn-222 would not be contained.
Calculator use notes
Most functions and settings are self-explanatory but we will highlight some key points below. The most important use instruction is this - if you make any change to the calculator settings (input values, units, multiplier settings, shielding material or thickness (etc), click Calculate to see the changes.
- Radionuclide selection - (will be expanded over next few weeks).
- Dose rate unit system - specify dose rate in SI (Gy/Sv) or Non SI (Rad / Rem). Note: since you may not be sure where the input dose rate is derived from, the calculator will output activity based on input absorbed dose rate (in air) and effective dose equivalent dose rate.
- Distance (from source) - can be specified in a range of SI and Non-SI units.
- Output activity unit system - choose the Bq (SI) or Ci (Non-SI) system for activity output.
- Output multiplier - apply micro, milli, base, kilo, mega etc to the output activity.
- Output format - choose from standard notation or scientific notation (i.e. 7423.9050 MBq or 7.424e+3 MBq).
- Shielding - choose if the calculation should consider shielding.
If the shielding option is picked then the following additional parameters are included:
- Material - choose the shielding material.
- Thickness - choose the shielding thickness (units will be based on the unit system selected).
Output
The output of the calculator is specified as follows.
- Activity (Absorbed Dose in Air): XXX Bq.
- Activity (Effective Dose Equivalent): YYY Bq.
In most practical situations the activity results will not differ by much - they account for an absorbed dose rate in air measurement, or a tissue equivalent measurement which might be provided from certain radiation dose rate equipment.
Why use this Ionactive calculator?
This calculator is offered as a radiation protection tool, it is not formal radiation safety advice. If you need formal advice then seek assistance from a Radiation Protection Adviser (RPA).
There are many resources out there on the web, including one particular popular internet calculator (of a similar fashion to this Ionactive calculator). The following may be noted:
- The Ionactive calculator is, in part based on ICRP 116 (which uses coefficients based on the FLUKA, GEANT4, MCNPX, and PHITS models). In addition, the calculation data is comparable with ANSI/ANS-6.1.1-2020, "Photon & Neutron Fluence-to-Dose Conversion Coefficients." Some more established calculators may use more dated resources.
Don't expect all similar calculators to output the same calculation result given the same inputs. In theory the output should be the same, in practice it depends on the methodology used. Differences will be most noticeable where shielding is applied - comparisons using basic TVT (10th value thickness), including those featured on the Ionactive website, can differ quite considerably since the use of TVT alone is a simplification. A slightly more rigorous discussion of this can be found in the supporting notes in our companion calculator: Radioactivity to Dose Rate Calculator (with shielding and dose rate ratio options).