Enter values to see results
—
Gy
—
mGy
—
rad
—
Sv
—
mSv
—
rem
—
mrem
Enter values to see results
—
Gy
—
mGy
—
rad
—
Sv
—
mSv
—
rem
—
mrem
The Radiation Dose Conversion Calculator converts between SI and conventional units of radiation absorbed dose and dose equivalent — Gray (Gy), milligray (mGy), rad, Sievert (Sv), millisievert (mSv), rem, and millirem (mrem). Understanding and correctly converting between these units is critical in radiation therapy, diagnostic imaging, nuclear industry safety, and regulatory compliance.
Two distinct but related quantities are covered. Absorbed dose (Gy, rad) measures the energy deposited per kilogram of matter: $$1 \text{ Gy} = 1 \text{ J/kg} = 100 \text{ rad}$$. Dose equivalent (Sv, rem) accounts for the biological effectiveness of different radiation types by applying a quality factor: $$H = D \times Q$$, where $$Q = 1$$ for gamma/beta radiation (making Gy and Sv numerically equal) and $$Q = 20$$ for alpha particles. The conversion factor between Sv and rem is the same: $$1 \text{ Sv} = 100 \text{ rem}$$.
This calculator provides the direct numerical conversion assuming a quality factor of 1 (gamma/X-ray/beta radiation), which is the most common scenario in medical imaging and radiation therapy. For alpha or neutron exposures, users must apply the appropriate quality factor separately after converting units.
All inputs are converted to gray as the reference unit, then all outputs are derived. Since the calculator assumes a radiation weighting factor of 1, the gray-to-sievert and rad-to-rem conversions are 1:1 numerically.
Absorbed Dose Conversions:
$$1 \text{ Gy} = 1000 \text{ mGy} = 100 \text{ rad}$$
Dose Equivalent Conversions:
$$1 \text{ Sv} = 1000 \text{ mSv} = 100 \text{ rem} = 100{,}000 \text{ mrem}$$
Cross-System Equivalence (for Q = 1):
$$1 \text{ Gy} = 1 \text{ Sv} \quad (\text{when } Q = 1)$$
$$1 \text{ rad} = 1 \text{ rem} \quad (\text{when } Q = 1)$$
The gray is defined as the absorption of one joule of ionizing radiation energy per kilogram of matter. The older unit rad (radiation absorbed dose) equals 0.01 Gy or 100 erg/g. Similarly, 1 rem = 0.01 Sv. These conversion factors — 100 rad per gray, 100 rem per sievert — are exact by definition.
The results show both absorbed dose and dose equivalent units simultaneously. Key reference values: a chest X-ray delivers about 0.02 mSv (2 mrem), a CT scan delivers 1–20 mSv (100–2000 mrem), the annual US background dose averages 3.1 mSv (310 mrem), and the occupational dose limit is 50 mSv/year (5 rem/year). Radiation therapy fractions typically deliver 1.8–2 Gy (180–200 rad) per session to the tumor volume. Understanding these scales helps contextualize converted values for medical, occupational, and public exposure assessments.
Inputs
Results
1 Gy = 100 rad = 1 Sv = 100 rem (for quality factor Q = 1). This is a very large dose — roughly half the lethal whole-body dose for humans.
Inputs
Results
A typical abdominal CT dose of 10 mSv equals 1 rem or 1000 mrem — about 3 times the annual natural background radiation dose.
The gray measures absorbed dose — the physical energy deposited per kilogram (J/kg). The sievert measures dose equivalent — the biological impact accounting for radiation type. They are related by $$H(\text{Sv}) = D(\text{Gy}) \times Q$$, where $$Q$$ is the quality factor (1 for gamma/beta, 20 for alpha). For gamma and X-ray radiation, 1 Gy = 1 Sv numerically.
The rad and rem are legacy CGS units that remain deeply embedded in US regulatory frameworks (NRC, EPA, OSHA) and medical practice. Many US radiation regulations specify limits in rem, and medical records often use rad for therapy doses. International bodies (ICRP, IAEA) use Gy and Sv exclusively, creating the need for frequent conversion.
The LD50/60 (dose lethal to 50% of exposed persons within 60 days without medical treatment) is approximately 3.5–4.5 Gy (350–450 rad) of whole-body acute gamma exposure. With modern medical care including antibiotics and blood transfusions, survival is possible at higher doses, up to about 6–8 Gy.
The quality factor (Q) accounts for different radiation types' biological damage per unit absorbed dose. For gamma, X-rays, and beta particles, $$Q = 1$$ (so Gy = Sv). For neutrons, $$Q = 5\text{–}20$$ depending on energy. For alpha particles, $$Q = 20$$. This means 0.05 Gy of alpha radiation equals 1 Sv of dose equivalent — 20 times more biologically damaging than the same absorbed dose of gamma radiation.
The ICRP recommends an occupational effective dose limit of 20 mSv/year (2 rem/year) averaged over 5 years, with no single year exceeding 50 mSv (5 rem). The US NRC limit is 50 mSv/year (5 rem/year). The public dose limit is 1 mSv/year (100 mrem/year) above natural background.
A typical posteroanterior chest X-ray delivers approximately 0.02 mSv (2 mrem) effective dose. For comparison: a dental X-ray is ~0.005 mSv, a mammogram ~0.4 mSv, a CT head ~2 mSv, and a CT abdomen/pelvis ~10 mSv. Natural background radiation in the US averages about 3.1 mSv/year.
Roboculator Team
The Roboculator Team explains calculations, planning tools, and practical formulas in clear language for real-life situations.
How helpful was this calculator?
Be the first to rate!
Magnetic Flux Conversion Calculator
Physics Unit Converters
Magnetic Field Strength Conversion Calculator
Physics Unit Converters
Radiation Activity Conversion Calculator
Physics Unit Converters
Energy Conversion Calculator
Physics Unit Converters
Power Conversion Calculator
Physics Unit Converters
Force Conversion Calculator
Physics Unit Converters
