Equivalent Radiation Dose Conversion Calculator
Written by Thierno Sadou Diallo, formula verified per our methodology • Last checked on 9/10/2026
To convert an equivalent radiation dose, it is reduced to sieverts (Sv), then converted into the desired unit: 1 Sv = 100 rem exactly. Example: a dose of 5 Sv equals 500 rem.
Explanation
The sievert (Sv), the SI unit of equivalent dose, measures the biological impact of ionizing radiation on an organism — unlike the gray (Gy), which measures only the physical energy deposited per unit mass (the absorbed dose), the sievert weights that energy by a factor that depends on the type of radiation (alpha particles, for example, are far more damaging at equal energy than X-rays). The rem ("röntgen equivalent man") is the equivalent historical CGS unit, still used in radiation protection in the United States: 1 Sv = 100 rem, exactly, by the same historical convention as the gray and the rad. In practice, doses encountered in everyday life are expressed in millisieverts or microsieverts: average natural exposure in France is about 3 mSv per year, and a chest X-ray delivers on the order of 0.02 mSv (20 µSv).
Example: a dose of 5 Sv
Inputs
Value: 5. Starting unit: Sv. Target unit: rem.
Calculation
1 Sv = 100 rem, by definition: so multiply by 100. 5 × 100 = 500 rem.
Result
A dose of 5 Sv equals 500 rem.
Frequently asked questions
What is the difference between the sievert and the gray?
The gray (absorbed dose) measures the physical energy deposited per kilogram of tissue, while the sievert (equivalent dose) weights that energy by a radiation quality factor to reflect its real biological impact. For X and gamma rays, that factor is 1 (1 Gy ≈ 1 Sv), but it is much higher for alpha particles. See our absorbed dose conversion calculator for the other quantity, in gray and rad.
What does a dose of a few millisieverts correspond to in everyday life?
Average natural exposure (cosmic radiation, radon, natural soil radioactivity) is about 3 mSv per year in France. A CT scan typically delivers 1 to 10 mSv depending on the area examined, versus about 0.02 mSv for a simple chest X-ray. This dose depends directly on the activity of the radiation source, expressed in becquerels or curies — see our radioactivity conversion calculator for that other quantity.
Why is the rem still used when the sievert is the SI unit?
The rem remains the reference regulatory unit in radiation protection in the United States, while nearly all other countries (including France) have used the sievert since the adoption of the International System. This calculator lets you easily switch between the two to compare documents or standards from different unit systems.
Does this calculator also convert the absorbed dose (gray/rad)?
No, deliberately: absorbed dose and equivalent dose are two distinct physical quantities that should never be mixed in the same converter, even though their numerical conversion factor is identical (100). Use our dedicated absorbed dose conversion calculator for the gray and the rad.