Home and public radon dose calculator
Use this calculator to estimate the annual effective dose to a member of the public from exposure to radon-222 (Rn-222) and its short-lived decay products in a home, school or other building.
The calculator can apply ICRP Publication 65, ICRP Publication 158, or compare both methods. ICRP Publication 158 presents age-specific dosimetric calculations but recommends a single rounded public radon coefficient for protection calculations in homes at all ages.
The person or scenario selected in the calculator records the context and sets a suggested occupancy. It does not change the dose conversion factor. Review the suggested hours and replace them with a more representative annual total where better information is available.
Radon concentration can be entered in Bq/m³ or pCi/L. Where pCi/L is selected, the value is converted internally using 1 pCi/L = 37 Bq/m³, and all dose calculations are completed using Bq/m³.
Before using the calculator
Enter a radon concentration that is representative of the building while the person is present. Enter only the hours spent at approximately that concentration. Where a person spends time in several rooms or buildings with materially different concentrations, calculate the exposures separately or use the Advanced Radon Exposure Profile Calculator.
The calculator suggests an equilibrium factor of F = 0.4. Only use another value where it has been measured or professionally justified.
Scope: This calculator covers radon-222 and its short-lived progeny only. It does not calculate dose from radon-220 (thoron) or thoron progeny. Do not enter an uncorrected combined radon/thoron measurement.
People exposed to radon as part of their work should use the Workplace Radon Dose Calculator.
Estimated annual effective dose
Calculation result
recommended public radon coefficient
Show calculation details
- Person or scenario
- Radon isotope scope
- Radon-222 and its short-lived progeny only; radon-220 (thoron) excluded
- Concentration entered
- Concentration used in the calculation
- Unit conversion
- Exposure time used
- Equilibrium factor used
- Radon exposure
- Equilibrium-equivalent exposure
- Potential alpha-energy exposure
- Reference dose conversion factor at F = 0.4
- Equilibrium-factor adjustment
- Dose conversion factor used
- Published method basis
DCFF = DCF0.4 × (F ÷ 0.4)
E = CRn-222 × t × DCFF
E is effective dose in mSv; CRn-222 is the radon-222 concentration in Bq·m⁻³; t is time in hours; DCF0.4 is the selected reference dose conversion factor at F = 0.4; and DCFF is that factor adjusted for the entered equilibrium factor.
Why is 5.56 × 10−6 shown?
The equilibrium-equivalent concentration represents the concentration of radon-222 in equilibrium with its short-lived progeny that would give the same potential alpha-energy concentration as the actual mixture. A concentration of 1 Bq·m⁻³ of equilibrium-equivalent radon corresponds to 5.56 × 10−9 J·m⁻³ of potential alpha energy.
Since 1 mJ = 10−3 J, this is 5.56 × 10−6 mJ·m⁻³ per Bq·m⁻³. When exposure time is included, the same numerical factor converts Bq·h·m⁻³ to mJ·h·m⁻³.
The potential alpha-energy exposure is displayed to show the relationship between equilibrium-equivalent radon exposure and potential alpha energy. The final effective dose is calculated using the reference dose conversion factor associated with the selected ICRP method.
How the calculation works
The calculator first determines the radon exposure:
Radon exposure = radon-222 concentration × exposure time
For the selected calculation method, it then uses a reference dose conversion factor stated at an equilibrium factor of F = 0.4. The reference factor is adjusted for the equilibrium factor entered:
Adjusted dose conversion factor = reference dose conversion factor × (selected F ÷ 0.4)
The annual effective dose is calculated as:
Effective dose = radon-222 concentration × exposure time × adjusted dose conversion factor
ICRP Publication 65
For this option, the calculator uses a public dose conversion factor of:
2.5 × 10⁻⁶ mSv per Bq·h·m⁻³ at F = 0.4
This is approximately equivalent to 4 mSv per working level month. The factor is adjusted in direct proportion to the equilibrium factor selected.
ICRP Publication 158
For this option, the calculator uses the ICRP Publication 158 recommended public radon coefficient of:
6.7 × 10⁻⁶ mSv per Bq·h·m⁻³ at F = 0.4
This corresponds to 3 mSv per mJ·h·m⁻³. Publication 158 presents age-specific modelled values for exposure in homes, but recommends the same rounded coefficient for public protection calculations at all ages. Selecting “child or young person” therefore records the exposure scenario and suggested occupancy; it does not substitute a separate child-specific coefficient.
Occupancy assumptions
The person or scenario selector provides a suggested annual occupancy:
- adult living in the home — 5,800 hours/year;
- child or young person living in the home — 7,000 hours/year;
- pupil or student using an educational building — 1,200 hours/year;
- visitor or user of a public building — 500 hours/year; and
- other member of the public — custom occupancy.
These are starting assumptions only. Replace them with a more representative annual exposure time where reliable information is available.
Home Action Level and Target Level
For homes, the calculator compares the entered concentration with the UK radon levels used to guide action:
- 200 Bq·m⁻³ Action Level: where this represents the annual-average concentration in the home, the radon level should be reduced.
- 100 Bq·m⁻³ Target Level: remediation should aim to reduce the annual-average concentration below this level where practicable. Householders between 100 and 200 Bq·m⁻³ should consider action, particularly where an occupant is a current or former smoker.
The Action Level and Target Level are concentration-based values. They are not applied by comparing the calculated dose with a dose limit.
Schools and other public buildings
The result for a pupil, student, visitor or other member of the public estimates public exposure only. It does not assess the occupational exposure of staff working in the building. Where employees may be exposed, their exposure should be considered separately using representative workplace measurements and the Workplace Radon Dose Calculator.
Breathing rate
No separate user-specific breathing rate is applied. The selected method uses a published public dose conversion convention or recommended public coefficient. The calculator should not be interpreted as individual respiratory dosimetry.
For scenarios involving several buildings or areas, different concentrations or equilibrium factors, or a sensitivity calculation using a selected breathing rate, use the Advanced Radon Exposure Profile Calculator.
Radon-220 (thoron)
Radon-220 and its progeny are not included. Thoron has a short half-life of approximately 56 seconds, so gas concentrations can vary sharply with distance from the emitting surface and the relationship between thoron gas and its progeny is highly location-dependent. The radon-222 default of F = 0.4 should not be applied to thoron.
Where thoron could make a material contribution, use equipment capable of distinguishing radon-222 from thoron and arrange a separate assessment based on appropriate thoron or thoron-progeny measurements.
Interpreting the result
This calculator provides an indicative annual effective dose estimate. Its reliability depends on the concentration, equilibrium factor and occupancy being representative. It does not replace representative radon measurements, professional remediation advice, or a formal assessment where one is required.
References and calculation basis
- ICRP Publication 65, Protection Against Radon-222 at Home and at Work.
- ICRP Publication 158, Dose Coefficients for Intakes of Radionuclides by Members of the Public: Part 1.
- IAEA guidance defining equilibrium-equivalent radon and the conversion of 1 Bq·m⁻³ EEC radon to 5.56 × 10⁻⁶ mJ·m⁻³.
- UKradon guidance on the home Action Level and Target Level.
Calculator version: 1.2
Calculation basis reviewed: July 2026