Radiation Dose Rate Calculator

Calculate radiation dose rate from source activity and distance using the inverse square law.

Inputs

Source Activity

Gamma Constant (Γ)

mSv·m²/(GBq·hr)

Distance from Source

Exposure Time

hours

Tab to move between fields

Results

Dose Rate

12.99 mSv/hr

Total Dose

12.99 mSv

Dose Rate12,987 μSv/hr

Total Dose1,298.7 mrem

Public Limit Distance161.16 m

Occupational Limit Distance36.04 m

Exceeds Occupational Limit1

Exceeds Public Limit1

Total Dose Usv12,987

How to Use This Calculator

Enter Source Activity, Gamma Constant (Γ), and Distance from Source.
Set Exposure Time.
Review Dose Rate (mSv/hr) and Total Dose (mSv).
Use Dose Rate (μSv/hr) and Total Dose (mrem) to inform your decision.
Use the chart to visualize the results and explore different scenarios by adjusting inputs.

What each input means

Source Activity: Radioactive source activity in becquerels. 1 Ci = 3.7×10¹⁰ Bq.
Gamma Constant (Γ): Specific gamma ray constant for the isotope. Cs-137: 0.0842, Co-60: 0.351, Ir-192: 0.130.
Distance from Source: Distance from the point source in meters.
Exposure Time: Duration of exposure in hours.

What each result means

Public Limit Distance: Distance for 1 mSv/yr (general public limit)
Occupational Limit Distance: Distance for 20 mSv/yr (occupational limit)
Exceeds Occupational Limit: 1 = Yes (>20 mSv/yr at 2000 hr/yr), 0 = No
Exceeds Public Limit: 1 = Yes (>1 mSv/yr at 2000 hr/yr), 0 = No

How this is calculated

Worked example, using the default values

Identify Input Parameters
4 parameters
Source Activity = 37000000000, Gamma Constant (Γ) = 0.351, Distance from Source = 1, Exposure Time = 1 = 4 input(s) provided
Calculate Dose Rate
Dose Rate = dr
12.987 = 12.987
Calculate Total Dose
Total Dose
12.987 = 12.987
Calculate Dose Rate
Dose Rate
12987 = 12987
Calculate Total Dose
Total Dose
1298.7 = 1298.7

The questions that sit next to this one — chosen by subject, including calculators filed under a different category.

Nuclear Science

Radiation Shielding Calculator

Calculate required shield thickness for target dose reduction using half-value and tenth-value layers.

Nuclear Science

Radioactive Decay Calculator

Calculate remaining radioactive activity from initial activity, half-life, and elapsed time.

Industrial Hygiene

Radiation Dose Calculator

Calculate occupational radiation dose from external gamma sources using inverse square law, shielding HVLs, and compare against OSHA/NRC annual dose limits.

Unit Conversion Expanded