Radiation Dose Equivalent Calculator

Enter the absorbed dose in grays (Gy), select the radiation type, and specify the exposure time to calculate the dose equivalent in sieverts (Sv). You'll also get the annual equivalent dose, radiation weighting factor used, and a safety assessment based on international exposure limits.

Gy

Energy deposited per unit mass of tissue (in grays)

Type of ionizing radiation determines the weighting factor

hours

Duration of radiation exposure

times

Number of times this exposure occurs annually

Results

Dose Equivalent (H)

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Dose Equivalent

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Dose Equivalent

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Radiation Weighting Factor (W_R)

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Annual Equivalent Dose

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% of Occupational Limit (20 mSv/yr)

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% of Public Limit (1 mSv/yr)

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Safety Assessment

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Results Table

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Frequently Asked Questions

What is dose equivalent in radiation physics?

Dose equivalent (H) measures the biological effect of ionizing radiation on human tissue. It is calculated by multiplying the absorbed dose (in grays) by a radiation weighting factor (W_R) that accounts for how damaging the specific type of radiation is. The result is expressed in sieverts (Sv).

What is the difference between absorbed dose and dose equivalent?

Absorbed dose (measured in grays) is the raw energy deposited per kilogram of matter, regardless of radiation type. Dose equivalent (measured in sieverts) adjusts for biological effectiveness — for example, 1 Gy of alpha radiation causes 20 times more biological damage than 1 Gy of gamma radiation, so their dose equivalents differ by a factor of 20.

What are ICRP radiation weighting factors?

The International Commission on Radiological Protection (ICRP) assigns weighting factors to different radiation types based on their relative biological effectiveness. Gamma rays and beta particles have W_R = 1, protons have W_R = 2, and alpha particles and heavy ions have W_R = 20. Neutron weighting factors vary from 2.5 to 20 depending on their energy.

What is the safe radiation dose limit for the general public?

The ICRP recommends an annual effective dose limit of 1 mSv (millisievert) per year for members of the general public, excluding medical and natural background radiation. For context, natural background radiation typically contributes about 2-3 mSv per year depending on location.

What is the occupational radiation dose limit?

For radiation workers, the ICRP recommends a limit of 20 mSv per year averaged over five consecutive years, with no single year exceeding 50 mSv. Additional limits apply to specific organs — for example, 150 mSv per year for the lens of the eye and 500 mSv per year for skin and extremities.

How do I convert sieverts to rem?

One sievert equals 100 rem. So 1 mSv = 100 mrem (millirem). The sievert is the SI unit used internationally, while the rem is an older unit still commonly used in the United States. This calculator provides results in both units for convenience.

Why do neutrons have different weighting factors at different energies?

Neutron biological effectiveness depends strongly on their kinetic energy. Thermal neutrons (very low energy) have W_R = 2.5, while fast neutrons in the 0.1-2 MeV range have W_R = 20 because they transfer energy most efficiently to hydrogen nuclei in tissue. At very high energies (>20 MeV), the weighting factor drops to 5 as interaction mechanisms change.

What are some common radiation dose examples?

A chest X-ray delivers about 0.02 mSv, a CT scan of the chest about 7 mSv, a transatlantic flight about 0.08 mSv, and natural background radiation averages 2-3 mSv per year. The dose limit for radiation workers is 20 mSv per year, and acute doses above 1,000 mSv (1 Sv) can cause radiation sickness.