How many rem is 1 sievert?

1 sievert equals exactly 100 rem. This is a defined conversion with no uncertainty: 1 Sv = 100 rem, 1 mSv = 100 mrem, 1 µSv = 0.1 mrem.

What is the difference between a sievert and a rem?

They measure the same physical quantity — equivalent radiation dose — in different unit systems. The sievert is the SI (metric) unit; the rem is the older CGS-based unit still used in the United States. 1 Sv = 100 rem.

What is a typical annual radiation dose in sieverts and rem?

Average background radiation in the US is about 3.1 mSv (310 mrem) per year from natural sources. Occupational limits are typically 50 mSv (5 rem) per year for radiation workers.

What is the difference between a sievert and a gray?

The gray (Gy) measures absorbed dose — the raw energy deposited per kilogram of tissue. The sievert multiplies absorbed dose by a radiation weighting factor to account for biological effectiveness. For x-rays and gamma rays the factor is 1, so 1 Gy = 1 Sv for those radiation types.

Why does the US still use rem instead of sieverts?

US nuclear regulatory standards (NRC, EPA, OSHA) were written in rem before the SI transition and have not been fully updated. The rem remains the legal unit in many US regulations, so conversions between Sv and rem are common in practice.

Sieverts to Rem Converter

Convert equivalent radiation dose between sieverts (Sv) and rem; 1 Sv = 100 rem, used in radiation protection and dosimetry.

Input

Dose in sieverts (Sv)

Result

Enter a value and click Convert

Common Dose Reference Values

Exposure scenario	Sieverts (Sv)	Rem
Chest X-ray (single)	0.1 mSv	10 mrem
Average annual US background	3.1 mSv	310 mrem
Occupational limit (annual)	50 mSv	5 rem
Whole-body CT scan	~10 mSv	~1,000 mrem
Radiation sickness threshold	1 Sv	100 rem
Lethal dose (LD50, acute)	~4–5 Sv	~400–500 rem

Summary

The sievert (Sv) is the SI unit of equivalent and effective radiation dose, accounting for both the absorbed energy and the biological effectiveness of the radiation type. The rem is the older unit still used in the United States for regulatory and occupational limits. The relationship is exact: 1 Sv = 100 rem, or equivalently 1 mSv = 100 mrem. This tool converts between the two in either direction and also shows millisievert and millirem values.

How it works

Select the direction: Sv to rem or rem to Sv.
Enter the dose value in the input field.
Click Convert to see the result.
The result shows the primary value plus millisievert and millirem equivalents.
Use the Copy button to copy the result to your clipboard.

Use cases

Convert a medical imaging dose report from millisieverts to millirem for US regulatory comparison.
Translate occupational exposure limits between ICRP (Sv) and NRC (rem) frameworks.
Cross-check annual dose limits: 50 mSv = 5 rem per ICRP and NRC guidelines.
Convert background radiation data from Sv to rem for public health communication.
Academic problems converting between SI and legacy radiation dose units.
Verify dosimeter readings across equipment using different unit systems.

Frequently Asked Questions

Last updated: 2026-07-14 · Reviewed by Nham Vu