Why can't I convert Bq to rem with just a fixed factor?

Becquerels count disintegrations per second but say nothing about the energy or biological effect per disintegration. Different isotopes emit different radiation types (alpha, beta, gamma) at different energies, producing vastly different doses per becquerel. The dose coefficient bridges the gap and is specific to the isotope, pathway, and organ.

What is the relationship between rem and sievert?

1 rem = 0.01 sievert (Sv), or equivalently 1 Sv = 100 rem. The rem is the older CGS unit; the sievert is the SI unit. Both measure effective or equivalent biological dose. Dose coefficients in the literature are usually published in Sv/Bq — multiply by 100 to get rem/Bq.

Where do I find the dose coefficient for my isotope?

The ICRP (International Commission on Radiological Protection) publishes dose coefficients in its publication series — ICRP-72 covers ingestion and inhalation for workers and members of the public. The US EPA Dose Factor Library and NRC Regulatory Guide 1.109 are also standard references. Always match the pathway (ingestion vs inhalation vs external) to your scenario.

What counts as a significant dose in rem?

Average US background exposure is about 0.3 rem (300 mrem) per year. The NRC public dose limit is 0.1 rem (100 mrem) per year from licensed operations. The occupational limit is 5 rem (5,000 mrem) per year. A single whole-body dose of 25 rem may cause temporary blood changes; 100 rem causes radiation sickness.

Do the preset coefficients in this tool apply to all tissues?

The presets are effective dose coefficients — they represent a whole-body average weighted by tissue sensitivity, as published by the ICRP for adult members of the public. Organ-specific absorbed dose coefficients differ and require looking up the target tissue separately.

One becquerel (Bq) equals one radioactive disintegration (nuclear decay) per second. It replaced the older curie (Ci), where 1 Ci = 3.7 × 10¹⁰ Bq. Typical household smoke detectors contain about 30,000 Bq of Am-241; a banana contains roughly 15 Bq from naturally occurring K-40.

Becquerels to Rem Converter

Enter activity in becquerels and a dose coefficient to calculate biological dose equivalent in rem, with common radionuclide presets.

Inputs

Dose equivalent (rem) = Activity (Bq) × Dose coefficient (rem/Bq)

Activity (Bq)

1 curie = 3.7 × 10¹⁰ Bq

Common Radionuclide Presets

Dose Coefficient (rem/Bq)

To convert Sv/Bq to rem/Bq: multiply by 100

Result

Enter activity and a dose coefficient, then click Calculate.

Context: US Annual Background ~300 mrem

Result as a percentage of 300 mrem/year US background dose.

Summary

Becquerels (Bq) measure radioactivity — the rate of nuclear disintegrations per second. Rem (Roentgen Equivalent Man) measures dose equivalent — the biological effect of radiation on human tissue. Converting from Bq to rem requires a dose coefficient (rem/Bq or Sv/Bq × 100), which depends on the specific radionuclide, the exposure pathway (ingestion, inhalation, or external), and the target tissue. This tool walks through the calculation step by step and includes preset coefficients for common isotopes.

How it works

Enter the activity in becquerels (Bq) — the quantity of radioactive material.
Select a common radionuclide preset or enter a custom dose coefficient (rem/Bq).
The tool multiplies activity × dose coefficient to give dose equivalent in rem.
Results are shown in rem, millirem (mrem), and sievert (Sv) simultaneously.
Compare against annual background radiation (~300 mrem/year in the US) for context.

Use cases

Estimate internal dose from ingesting or inhaling a known activity of a radionuclide.
Cross-check hand calculations in radiation protection and nuclear safety reviews.
Teach the difference between radioactivity (Bq) and dose equivalent (rem/Sv).
Convert published Sv/Bq coefficients to the older rem/Bq system for legacy reports.
Quickly assess whether a measured activity poses a significant dose concern.
Compare doses from different radionuclides at the same activity level.

Frequently Asked Questions

Last updated: 2026-07-14 · Reviewed by Nham Vu