Sieverts to Becquerels Converter
Select a radionuclide and pathway, enter dose in sieverts, and get the corresponding activity in becquerels using published ICRP coefficients.
Inputs
Activity (Bq) = Dose (Sv) ÷ Dose coefficient (Sv/Bq)
Quick examples
Results
Select a nuclide, pathway, and dose, then press Calculate
Activity (Bq)
Calculation details
Reference: activity that delivers 1 mSv (ingestion)
Based on ICRP-72 effective dose coefficients for an adult member of the public.
| Radionuclide | Coeff. (Sv/Bq) | Activity for 1 mSv | Notes |
|---|---|---|---|
| H-3 (tritium) | 1.8 × 10-11 | 55.6 GBq | Very low hazard per Bq; large activity needed for dose |
| Tc-99m | 2.2 × 10-11 | 45.5 GBq | Short half-life (6 h); used in nuclear medicine |
| Mn-54 | 7.1 × 10-10 | 1.41 GBq | Activation product in reactor cooling water |
| C-14 | 5.8 × 10-10 | 1.72 GBq | Cosmogenic; low energy beta emitter |
| K-40 | 6.2 × 10-9 | 161 MBq | Naturally present in food and human body |
| Fe-55 | 3.3 × 10-10 | 3.03 GBq | Industrial and nuclear activation product |
| Co-60 | 3.4 × 10-9 | 294 MBq | High-energy gamma emitter; used in radiotherapy |
| Cs-137 | 1.3 × 10-8 | 76.9 MBq | Major fission product; Chernobyl / Fukushima fallout |
| I-131 | 2.2 × 10-8 | 45.5 MBq | Concentrates in thyroid; nuclear accident concern |
| Sr-90 | 2.8 × 10-8 | 35.7 MBq | Bone-seeking beta emitter; long half-life (28.8 y) |
| U-238 | 4.5 × 10-8 | 22.2 MBq | Natural uranium; alpha emitter depositing in kidney |
| Th-232 | 2.3 × 10-7 | 4.35 MBq | Primordial nuclide; very long half-life (14.05 Gy) |
| Ra-226 | 2.8 × 10-7 | 3.57 MBq | Uranium decay chain; historically used in dials |
| Am-241 | 2.0 × 10-7 | 5.00 MBq | Alpha emitter; used in smoke detectors (trace amounts) |
| Po-210 | 1.2 × 10-6 | 833 kBq | Extremely hazardous per Bq; alpha emitter, very high LET |
Dose coefficients from ICRP Publication 72 (1996) for adult ingestion pathway. This tool is for educational purposes only — not for medical, regulatory, or occupational dose assessment.
Sv and Bq: two different measurements
Becquerel (Bq)
One nuclear disintegration per second. It describes the activity of a radioactive source — how frequently atoms are decaying. A high Bq count tells you the source is busy decaying, but says nothing by itself about biological risk.
Sievert (Sv)
Effective dose: the biological impact of radiation on the whole body, weighted for the type of radiation and the sensitivity of affected tissues. 1 Sv = 1 J/kg multiplied by quality and tissue weighting factors. Annual occupational limit is typically 20 mSv.
Why no fixed ratio
1 MBq of H-3 ingested gives roughly 18 µSv. The same activity of Po-210 ingested gives about 1,200 mSv — over 60,000 times higher. Decay energy, radiation type, half-life, and organ uptake all drive the difference.
Summary
Select a radionuclide and pathway, enter dose in sieverts, and get the corresponding activity in becquerels using published ICRP coefficients.
How it works
- Select a radionuclide from the dropdown — common choices include I-131, Cs-137, H-3, Ra-226, and others.
- Choose an exposure pathway: ingestion (swallowing) or inhalation (breathing).
- Enter the dose in sieverts (Sv), millisieverts (mSv), or microsieverts (µSv).
- The tool divides the dose by the ICRP effective dose coefficient (Sv/Bq) to produce activity in becquerels.
- Results are displayed in Bq, kBq, MBq, GBq, and curie equivalents.
- For regulatory, occupational, or medical decisions always consult a qualified health physicist using authoritative dose calculation software.
Use cases
- Back-calculating how much activity of a specific radionuclide would have caused an observed dose.
- Cross-checking hand calculations in health physics coursework.
- Understanding the activity levels that correspond to regulatory dose limits.
- Education on why the same dose from different nuclides implies vastly different activity amounts.
- Comparing nuclide-specific intake scenarios in environmental dose assessments.
- Estimating source activity from occupational or public dose records.