Instantly convert radiation dose units — sievert, millisievert, gray, rad, rem, and more — for both absorbed dose and equivalent dose.
Radiation dose measures the energy deposited by ionizing radiation into matter. In practice, two closely related quantities are used. Absorbed dose is measured in gray (Gy) or the older unit rad and represents the energy absorbed per kilogram of tissue. Equivalent dose is measured in sievert (Sv) or the older unit rem — it is the absorbed dose multiplied by the radiation weighting factor W_R, which reflects the biological effects of different radiation types. For X-rays, gamma rays, and electrons — the most common sources in medical and environmental contexts — W_R = 1, so 1 Gy is numerically equal to 1 Sv.
This converter handles all common dose units in real time, organized into two groups: absorbed dose (gray family and rad) and equivalent/effective dose (sievert family, rem/millirem/BED). Enter a value, select the source unit — and all other units update instantly.
Every conversion uses sievert (Sv) as the internal base unit, assuming W_R = 1. To convert one unit to another, the source value is multiplied by the Sv factor of the source unit then divided by the factor of the target unit:
Where f represents each unit's conversion factor to sievert. E.g.: 1 mSv = 0.001 Sv, 1 rem = 0.01 Sv, 1 BED ≈ 0.1 µSv = 1 × 10⁻⁷ Sv.
Scale factor
Absorbed ↔ Equivalent
Quick Reference
A standard chest X-ray delivers approximately 0.1 mSv effective dose — equivalent to about 10 days of average US background radiation. In microsieverts that's 100 µSv; in millirem, 10 mrem.
The average American receives about 3.1 mSv per year from natural sources — roughly half from radon in homes and buildings, with the rest from cosmic radiation, terrestrial gamma, and internal sources. Residents of high-altitude states like Colorado receive more due to thinner atmospheric shielding. The US National Council on Radiation Protection and Measurements (NCRP) and the NRC track national exposure levels.
The 1979 Three Mile Island accident in Pennsylvania is estimated to have exposed nearby residents to an average of about 1 mrem (0.01 mSv) — well below the annual limit. Today, US nuclear power plant workers are subject to an annual effective dose limit of 5 rem (50 mSv) under 10 CFR Part 20 (NRC regulations), with an ALARA target far below that.
A screening mammogram delivers approximately 0.4 mSv effective dose — about 4 times a chest X-ray but far below annual background levels. In millirem that's 40 mrem. The benefit of early breast cancer detection far outweighs the small radiation risk for recommended screening populations.
Enter the dose value you want to convert in the input field. Decimal values and large numbers are fully supported.
Select the source unit from the dropdown menu. All 11 units are listed with their full name and symbol.
The converter multiplies the input value by the source unit's Sv factor to get a Sv intermediate value, then divides by each target unit's factor.
Results are displayed in two groups: Absorbed Dose (gray + rad) and Equivalent/Effective Dose (sievert + rem/millirem/BED).
Very large or very small results are shown in scientific notation (e.g. 1.23 × 10⁻⁷) for optimal readability.
For X-rays and gamma rays (the most common medical and environmental sources), W_R = 1, so 1 Gy = 1 Sv. This converter applies that assumption throughout.
Radiation therapy doses are typically expressed in gray (Gy) or centigray (cGy). A standard daily fractionated dose of 2 cGy equals exactly 20 mGy.
In radiation protection and environmental monitoring, millisievert (mSv) or microsievert (µSv) are typically used.
Banana Equivalent Dose (BED) is an informal unit — 1 banana ≈ 0.1 µSv — useful for explaining low doses to the general public. It is not an official SI unit.
Rem and millirem are still widely used in the US for regulatory reporting under NRC and EPA rules. 1 rem = 10 mSv and 1 mrem = 10 µSv.
Gray (Gy) measures absorbed dose — the physical energy (in joules) deposited per kilogram of any matter. Sievert (Sv) measures equivalent dose — the absorbed dose multiplied by the radiation weighting factor W_R, which reflects the biological impact of each radiation type. For X-rays, gamma, and electrons W_R = 1, so Gy and Sv are numerically equal. For neutrons or alpha particles, W_R > 1.
The radiation weighting factor (W_R) depends on radiation type and cannot be determined from the dose value alone. This converter uses W_R = 1, which is correct for gamma rays, X-rays, and electrons — the radiation type encountered in the vast majority of medical, occupational, and environmental situations.
A chest X-ray delivers about 0.1 mSv (100 µSv or 10 mrem) effective dose — equivalent to roughly 10 days of average US background radiation (3.1 mSv/yr). A chest CT is significantly higher, typically 5–8 mSv (500–800 mrem).
Under NRC regulations (10 CFR Part 20), the annual whole-body effective dose limit for radiation workers is 5 rem (50 mSv). The ALARA principle requires doses to be kept as low as reasonably achievable, and most workers receive far less than this limit. Members of the public are limited to 100 mrem (1 mSv) per year from licensed nuclear facilities.
The Banana Equivalent Dose (BED) is an informal unit equal to approximately 0.1 µSv (1 × 10⁻⁷ Sv). It represents the tiny extra dose from eating one banana, due to naturally occurring potassium-40. It's used for educational purposes to put low doses in context; it is not an official SI or ICRU unit.
Rem (Roentgen Equivalent Man) and millirem (mrem) are older CGS units of equivalent dose still widely used in the US for regulatory reporting under NRC and EPA rules. The conversion is straightforward: 1 rem = 0.01 Sv = 10 mSv and 1 mrem = 0.001 rem = 10 µSv.
This converter assumes radiation weighting factor W_R = 1 (applicable to gamma rays, X-rays, and electrons). For other radiation types (neutrons, protons, alpha particles, heavy ions), sievert values differ from gray values. For clinical or occupational dose assessments, always consult a qualified medical physicist or radiation protection specialist.