Are rad and becquerel measuring the same thing?

No. Rad (and its SI equivalent, gray) measures absorbed dose — energy deposited per unit mass of tissue (1 rad = 0.01 J/kg). Becquerel measures radioactivity — the rate of nuclear decays per second. To link them you must specify radiation type, tissue mass, and exposure time.

What is the conversion formula?

Absorbed dose (Gy) = Activity (Bq) × Energy per decay (J) × Time (s) / Mass (kg). Rearranging: Activity (Bq) = Dose (Gy) × Mass (kg) / (Energy per decay (J) × Time (s)). This tool performs that rearrangement for you.

Why does the answer change when I select a different radiation type?

Different particles deposit different amounts of energy per decay. An alpha particle releases about 5 MeV, while an average beta particle releases roughly 0.5 MeV. A lower energy per decay means a higher activity is needed to achieve the same total dose.

What assumptions does this tool make?

The tool assumes all emitted energy is absorbed uniformly within the specified mass, with no geometry, shielding, or isotope-specific corrections. For precision dosimetry, use Monte Carlo transport codes or vendor-supplied dose-conversion factors.

How does becquerel relate to curie?

1 curie (Ci) = 37,000,000,000 becquerels (3.7 × 10^10 Bq). The curie was defined as the activity of 1 gram of radium-226. Modern practice uses becquerels (the SI unit), but curies remain common in US industrial and medical contexts.

What is a typical lab source activity in becquerels?

A common educational check source might be 3.7 kBq (0.1 µCi). A nuclear medicine PET scan uses roughly 400 MBq of F-18. A hospital radiotherapy source can be in the range of 10–400 TBq (terabecquerels).

Rad to Becquerels Converter

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

Given an absorbed dose in rad, radiation type, tissue mass, and exposure time, estimate the source activity in becquerels that would produce that dose.

Input Parameters

Absorbed Dose (rad)

1 rad = 0.01 gray (Gy) = 0.01 J/kg absorbed.

Radiation Type

Sets mean energy per decay. Values are representative; use isotope-specific data for precision work.

Absorbing Mass

Typical whole-body mass: 70 kg = 70,000 g.

Exposure Duration

Source Activity

Activity (Bq)

—

Activity (scaled)

—

Activity (curie)

—

Energy per decay used

—

Reference Activities

Check source (lab)	~3.7 kBq
Smoke detector (Am-241)	~37 kBq
PET scan (F-18)	~400 MBq
Radiotherapy source	10–400 TBq

How the calculation works

Dose (Gy) = Activity (Bq) × Energy/decay (J) × Time (s) ÷ Mass (kg). Rearranged: Activity (Bq) = Dose (Gy) × Mass (kg) ÷ (Energy/decay (J) × Time (s)). The input dose in rad is first converted to gray (1 rad = 0.01 Gy).

Assumes all emitted energy is absorbed uniformly within the stated mass (no geometry, shielding, or scatter corrections). For precision dosimetry, use Monte Carlo transport codes or isotope-specific dose-conversion factors.

Summary

Given an absorbed dose in rad, radiation type, tissue mass, and exposure time, estimate the source activity in becquerels that would produce that dose.

How it works

Enter the absorbed dose in rad you want to convert.
Select the radiation type (gamma, beta, alpha, neutron) to apply the correct mean energy per decay.
Enter the mass of tissue that absorbed the radiation in grams or kilograms.
Set the exposure duration over which the dose was received.
The tool solves the dose equation in reverse: Activity (Bq) = Dose (Gy) × Mass (kg) / (Energy per decay (J) × Time (s)).
Results appear in becquerels (Bq) with SI prefix scaling for readability.

Use cases

Back-calculate source strength from a measured absorbed dose in health physics training.
Cross-check manual dosimetry calculations in nuclear engineering coursework.
Understand the quantitative link between source activity and tissue dose.
Compare required source activities for different radiation types at the same dose target.
Convert reference dose figures into activity units for radiation safety planning.
Verify nuclear medicine activity prescriptions against intended tissue dose.

Frequently Asked Questions

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