Why do I need to pick a radionuclide to convert Bq to Sv?

Unlike converting between two fixed units, Bq and Sv are not directly proportional by a universal constant. The effective dose per becquerel depends on the specific isotope (its decay energy, radiation type, and half-life), the exposure pathway (ingestion versus inhalation), and the distribution of the radionuclide in body tissues. Without knowing the nuclide, the conversion is undefined.

What does "effective dose coefficient" mean?

The effective dose coefficient (Sv/Bq) is the committed effective dose per unit intake of a given radionuclide via a specific pathway. It is calculated by summing, over all body organs, the product of absorbed dose per unit activity, the radiation weighting factor, and the tissue weighting factor. Values are published by the International Commission on Radiological Protection (ICRP).

What is the annual background radiation dose?

The global average effective dose from natural background radiation is about 2.4 mSv per year (2,400 µSv), according to UNSCEAR. This includes contributions from cosmic radiation, terrestrial gamma radiation, radon inhalation, and naturally occurring radionuclides in food and water.

Is this tool suitable for medical or regulatory decisions?

No. This tool is for educational purposes only. ICRP dose coefficients are population averages and do not account for individual physiology, age at exposure, or specific intake scenarios. For any regulatory, occupational, or clinical dose assessment, consult a qualified health physicist or medical physicist using authoritative dose calculation software.

What is the difference between sievert and gray?

The gray (Gy) measures absorbed dose — the physical energy deposited per unit mass of tissue (1 J/kg). The sievert (Sv) measures effective dose — absorbed dose weighted by radiation quality factor and tissue sensitivity. For X-rays and gamma rays the weighting factor is 1, so Gy and Sv are numerically equal for those radiation types; for alpha particles the weighting factor is 20.

Where do the dose coefficients in this tool come from?

Coefficients are taken from ICRP Publication 72 (1996) "Age-Dependent Doses to Members of the Public from Intake of Radionuclides" and represent committed effective dose for an adult member of the public per unit activity ingested or inhaled. Values are rounded to 2 significant figures for display.

Becquerels to Sieverts Converter

Name: Becquerels to Sieverts Converter
Availability: InStock
Author: Nham Vu

Select a radionuclide and pathway, enter activity in becquerels, and get effective dose in sieverts using published ICRP coefficients.

Inputs

Effective dose (Sv) = Activity (Bq) × Dose coefficient (Sv/Bq)

Radionuclide

Exposure pathway

Ingestion (swallowing) Inhalation (breathing)

Activity

Quick examples

Results

Select a nuclide, pathway, and activity, then press Calculate

Bq, Sv, and why nuclide choice matters

Becquerel (Bq)

One disintegration per second. It describes how active a source is, not how dangerous. A highly active source can be nearly harmless (short-lived, weak emitter) or very hazardous (long-lived, alpha emitter in organ tissue).

Sievert (Sv)

Effective dose, weighted for radiation type and organ sensitivity. 1 Sv = 1 J/kg × quality × tissue factors. The global annual background is about 2.4 mSv; occupational limits are typically 20 mSv/year.

Why nuclide matters

1 MBq of H-3 ingested gives roughly 18 µSv. The same activity of Po-210 ingested gives about 1,200 mSv — more than 60,000 times higher. Decay energy, radiation type, and organ uptake drive the difference.

Dose coefficients sourced from ICRP Publication 72 (1996) for adults. This tool is for educational purposes only — not for medical, regulatory, or occupational dose assessment.

Summary

Select a radionuclide and pathway, enter activity in becquerels, and get effective dose in sieverts 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 activity in becquerels (Bq), kiloBq, MegaBq, etc.
The tool multiplies activity by the ICRP effective dose coefficient (Sv/Bq) to produce effective dose.
Results are shown in sieverts, millisieverts, microsieverts, and as a fraction of annual background dose.
For precise regulatory or medical use, always consult authoritative ICRP/EPA publications and a qualified health physicist.

Use cases

Estimating committed effective dose from accidental radionuclide ingestion.
Education and training in radiation protection principles.
Cross-checking hand calculations in nuclear medicine or health physics coursework.
Comparing nuclide-specific dose contributions in environmental dose assessments.
Understanding why 1 Bq of different nuclides produces vastly different doses.
Rough screening of potential dose from food or water contamination incidents.

Frequently Asked Questions

Last updated: 2026-07-22 · Reviewed by Nham Vu