What is the difference between absorbed dose, equivalent dose, and effective dose?

Absorbed dose (Gray, Gy) measures energy deposited per kilogram of tissue with no regard to biological effect. Equivalent dose (Sievert, Sv) multiplies absorbed dose by the radiation weighting factor (wR) to account for how damaging a given radiation type is. Effective dose (Sievert, Sv) further multiplies by the tissue weighting factor (wT) to reflect the relative cancer risk of each organ, then sums across all irradiated organs.

Where do the weighting factors come from?

Radiation weighting factors (wR) and tissue weighting factors (wT) are published by the International Commission on Radiological Protection (ICRP) in Publication 103 (2007). They are derived from epidemiological data and radiobiological experiments and are updated periodically as new evidence emerges.

Why do tissue weighting factors sum to 1.0?

The wT values are normalized so that uniform whole-body irradiation produces an effective dose numerically equal to the equivalent dose to any single tissue. This makes effective dose a single number that reflects overall stochastic risk regardless of which organs were irradiated.

Can I use Gray and Sievert interchangeably for X-rays?

For X-rays and gamma rays the radiation weighting factor wR = 1, so 1 Gy of absorbed dose equals 1 Sv of equivalent dose numerically. However they are conceptually different quantities and should not be used interchangeably for other radiation types (e.g. protons wR = 2, alpha particles wR = 20).

Is this tool suitable for regulatory dose reporting?

This tool provides estimates for reference and educational use. Regulatory dose assessments require calibrated dosimetry, facility-specific geometry, and review by a qualified health physicist or medical physicist.

Effective Dose Calculator

Apply ICRP 103 radiation and tissue weighting factors to convert absorbed dose (Gy) to effective dose (mSv).

Radiation Type

Select radiation type

Selected wR: 1

Absorbed Dose Unit

mGy (milligray) Gy (gray) rad

Organ / Tissue Absorbed Doses

Leave blank or zero to exclude an organ.

Effective Dose Breakdown

Enter organ doses and click Calculate.

Total Effective Dose wR = 1

Millisievert (mSv)

Sievert (Sv)

millirem (mrem)

Organ Breakdown (ICRP 103)

Organ / Tissue	wT	H (mSv)	wT × H

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Summary

Effective dose accounts for both the biological effectiveness of different radiation types and the radiosensitivity of irradiated tissues. This tool applies ICRP Publication 103 radiation weighting factors (wR) and tissue weighting factors (wT) to convert absorbed dose in Gray (Gy) to effective dose in millisieverts (mSv). You can evaluate a single organ or sum contributions across multiple tissue types for whole-body dose assessment.

How it works

Select the radiation type to load its ICRP 103 radiation weighting factor (wR).
Enter the mean absorbed dose to one or more organs in milligray (mGy).
The tool multiplies each organ dose by wR to get the equivalent dose (mSv).
Each equivalent dose is then multiplied by the organ tissue weighting factor (wT).
Weighted organ doses are summed to give the total effective dose (mSv).
Use the Copy Result button to export the full breakdown for reporting.

Use cases

Estimating patient effective dose from diagnostic imaging (CT, X-ray, nuclear medicine).
Occupational dose assessment for radiation workers exposed to mixed fields.
Academic exercises in health physics and medical radiation science courses.
Comparing doses from different radiation types on a common biological scale.
Quick ALARA check before submitting a dose report to regulators.
Teaching the distinction between absorbed dose, equivalent dose, and effective dose.
Validating Monte Carlo simulation outputs against ICRP 103 benchmarks.
Radiation protection planning for industrial radiography procedures.

Frequently Asked Questions

Last updated: 2026-06-15 · Reviewed by Nham Vu