Radiation Dose Calculator
Compute effective radiation dose in sieverts from absorbed dose, radiation weighting factor, and tissue weighting factor, following ICRP-103 conventions. Useful for radiological protection planning, medical imaging dose reviews, and occupational exposure assessments.
Last updated: May 2026
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About this calculator
Effective dose (E, in sieverts, Sv) is the quantity used worldwide to express the long-term cancer and hereditary risk of radiation exposure. The formula is E = D × w_R × w_T, where D is absorbed dose in gray (Gy = J/kg), w_R is the radiation weighting factor (dimensionless) that accounts for how biologically damaging a particular radiation type is per unit absorbed energy, and w_T is the tissue weighting factor (dimensionless) that reflects the relative radiosensitivity of different organs. The result is in sieverts (Sv) when D is in Gy; 1 Sv = 1 J/kg of risk-weighted exposure. ICRP-103 (2007) defines the standard weighting factors: w_R = 1 for photons (X-rays, gamma) and electrons (beta) at all energies; w_R = 2 for protons and charged pions; w_R = 20 for alpha particles, fission fragments, and heavy ions; w_R for neutrons follows a continuous energy function ranging from 2.5 (very low or very high energy) to 20 (at peak energy near 1 MeV). Tissue weighting factors sum to 1 across all organs: bone marrow = 0.12, colon = 0.12, lung = 0.12, stomach = 0.12, breast = 0.12, gonads = 0.08, thyroid = 0.04, esophagus = 0.04, bladder = 0.04, liver = 0.04, brain = 0.01, salivary glands = 0.01, skin = 0.01, bone surface = 0.01, and 'remainder' = 0.12 spread across 14 other tissues. Edge cases: the calculator computes single-organ effective dose contribution; for whole-body or multi-organ exposures, sum the contributions across all exposed tissues. The formula is for stochastic risk (cancer); for deterministic effects (acute radiation syndrome at high doses), use equivalent dose to specific organs without tissue weighting. Effective dose is not measured directly — it is calculated from physical absorbed-dose measurements via these conventional factors.
How to use
Example 1 — chest CT scan to lungs. Absorbed dose to lung tissue D = 0.012 Gy (12 mGy, typical for a chest CT). Radiation type: X-rays, w_R = 1. Tissue: lung, w_T = 0.12. Step 1: E = 0.012 × 1 × 0.12 = 0.00144 Sv = 1.44 mSv. Verify against typical published chest-CT effective dose ranges of 5–10 mSv (whole-body summed across all exposed organs); the per-organ contribution of 1.44 mSv for lung alone is consistent with lung being one of several exposed tissues. Example 2 — alpha contamination of bone marrow (worker scenario). D = 0.005 Gy (5 mGy) absorbed in red bone marrow. Radiation: alpha particles, w_R = 20. Tissue: bone marrow, w_T = 0.12. Step 1: E = 0.005 × 20 × 0.12 = 0.012 Sv = 12 mSv. Verify by checking the comparison: the same 5 mGy as gamma to bone marrow would give 0.005 × 1 × 0.12 = 0.6 mSv — a factor of 20 lower, exactly the w_R ratio for alpha vs. photons. This illustrates why alpha-emitting internal contaminants (radon decay daughters, ingested plutonium) are vastly more dangerous than equivalent external gamma exposure.
Frequently asked questions
What are the key differences between absorbed dose, equivalent dose, and effective dose?
These three quantities form a hierarchy in radiation protection. Absorbed dose (D, in Gy) is purely physical — the energy deposited per unit mass of tissue, identical regardless of radiation type or organ. Equivalent dose (H_T, in Sv) is D × w_R, weighting absorbed dose by the radiation type's biological damage per unit energy; an alpha-irradiated organ has 20× the equivalent dose of the same Gy delivered by gamma rays. Effective dose (E, in Sv) is the sum across organs of H_T × w_T, weighting equivalent doses by each organ's radiosensitivity; it represents whole-body risk and is the quantity used in dose limits. The three quantities share the same name unit (Sv, but absorbed dose is in Gy not Sv) only because the weighting factors are dimensionless, and confusing them is one of the most common errors in radiation protection.
How do ICRP-103 (2007) tissue weighting factors differ from earlier ICRP-60 (1990) values?
ICRP-60 (1990) used 12 tissues plus a 'remainder' group with w_T values like 0.20 for gonads, 0.12 for bone marrow/colon/lung/stomach, 0.05 for bladder/breast/liver/esophagus/thyroid, and 0.01 for bone surface/skin. ICRP-103 (2007) refined the factors based on updated cancer-incidence data: gonads were reduced from 0.20 to 0.08 (lower hereditary risk than originally estimated), breast was raised from 0.05 to 0.12, brain and salivary glands were added at 0.01 each, and the 'remainder' group was expanded to 14 specific tissues each receiving 1/14 of the 0.12 remainder total. Regulators in most countries have adopted ICRP-103, but some legal frameworks (US 10 CFR 20, for example) still reference older values. Always check which version your jurisdiction uses; a chest dose can differ by 30–40% between the two systems.
What are the annual radiation dose limits for workers and the general public?
ICRP-103 and most national regulators set the occupational effective dose limit at 20 mSv/year averaged over 5 years, with no single year exceeding 50 mSv. The general public limit is 1 mSv/year above natural background, with allowance for higher single-year doses in special circumstances. Additional equivalent-dose limits apply to specific tissues: lens of the eye 20 mSv/year (occupational, reduced from 150 mSv after cataract evidence), skin 500 mSv/year, hands and feet 500 mSv/year. Pregnant workers must keep fetal dose below 1 mSv for the remainder of pregnancy after declaration. For comparison, natural background averages 2.4 mSv/year worldwide (ranging from 1 to 10 mSv based on geography and altitude); a single chest CT is ~5–10 mSv; transatlantic flights add ~0.05 mSv per flight. The ALARA principle (As Low As Reasonably Achievable) requires reducing doses below these limits where practical.
What are common mistakes when computing effective dose?
The most frequent mistake is confusing units: reporting D in milligray but plugging in the milli factor as if it were gray, producing values 1000× too small or too large. Another error is treating effective dose as a measured quantity — it is a calculated weighted sum, not something a dosimeter reads directly; what dosimeters measure is operational quantities (personal dose equivalent H_p(10)) that approximate E. People sometimes use the wrong w_R for neutrons by picking a single value when the ICRP-103 neutron w_R is a continuous function of energy ranging from 2.5 to 20. Mixing ICRP-60 and ICRP-103 weighting factors in the same calculation produces a frankenfigure that matches no regulatory standard. Forgetting to sum across exposed organs when reporting whole-body E (using just one organ's contribution as if it were the total) understates the dose, sometimes by 5–10×. Finally, applying effective dose for high-dose acute exposures (>1 Gy) is misleading — at those levels, deterministic tissue damage dominates and equivalent dose to specific organs is the relevant quantity.
When should I NOT use this calculator?
Skip effective-dose calculations for acute high-dose scenarios above ~1 Gy where deterministic effects (burns, ARS, organ failure) dominate over stochastic cancer risk — those need organ equivalent dose, time-resolved exposure curves, and clinical triage models like the RTR (Response and Recovery) protocol. Do not use it for medical-imaging optimization at the patient-specific level — modern guidance prefers DRLs (Diagnostic Reference Levels) and SSDE (Size-Specific Dose Estimates) rather than a single effective dose number that hides patient-size and protocol effects. Avoid it for radon dose: the ICRP uses a separate dose-conversion convention (mSv per WLM) that bypasses the standard w_R = 20 alpha factor. For internal contamination from inhaled or ingested radionuclides, use committed effective dose calculations from ICRP-130/137 dose-coefficient tables, not the simple external-exposure formula here. Finally, effective dose is not designed for individual risk prediction — it is a regulatory protection quantity averaged across populations, so do not use it to tell a specific patient their personal cancer risk from a CT scan.