Dose Equivalent (CGS) Converter

Millirem vs Microrem Explained

A millirem (mrem) is 1,000 times larger than a microrem (μrem). This page compares these legacy radiation dose units, explains their relationship to sieverts, and includes a bidirectional converter.

mrem
×1,000
μrem
1 mrem = 1,000 μrem

How Millirem and Microrem Compare

The millirem (mrem) and microrem (μrem) are CGS-based units of dose equivalent. 1 mrem = 1,000 μrem. The rem (Roentgen Equivalent Man) is the non-SI counterpart of the sievert: 1 rem = 10 mSv, so 1 mrem = 10 μSv and 1 μrem = 0.01 μSv.

The rem is still widely used in the United States for regulatory dose limits, radiation worker badges, and environmental monitoring reports. The NRC sets public dose limits at 100 mrem/yr (100,000 μrem/yr) and occupational limits at 5,000 mrem/yr (5,000,000 μrem/yr).

This page includes a bidirectional mrem ↔ μrem converter, a reference chart, and FAQ covering common rem-based radiation scenarios.

Millirem to Microrem Conversion Formula

μrem = mrem × 1,000

To convert mrem → μrem: multiply by 1,000. To convert μrem → mrem: divide by 1,000. The factor is 10³, identical to all milli-to-micro conversions.

To convert to SI: 1 mrem = 0.01 mSv = 10 μSv. 1 μrem = 0.01 μSv = 10 nSv.

Millirem vs Microrem Reference Chart

Millirem Microrem Example Real-World Use

The comparison chart shows common doses in both mrem and μrem, with sievert equivalents for reference.

Frequently Asked Questions

What is the difference between mrem and μrem?

Both measure dose equivalent using the CGS rem unit. A millirem (mrem) is 1,000 times larger than a microrem (μrem). 1 mrem = 1,000 μrem = 0.01 mSv = 10 μSv.

Why does the US still use rem instead of sievert?

US regulations (NRC, EPA, DOE) were written using rem before the SI system was adopted internationally. Converting all regulatory documents and dosimetry records to sieverts would be complex, so the rem remains the de facto standard in US radiation protection.

How do I convert mrem to mSv?

Divide by 100. 1 mrem = 0.01 mSv. For example, the US public limit of 100 mrem/yr = 1 mSv/yr, matching the international ICRP recommendation.

What is the US annual radiation dose limit?

The NRC sets the public dose limit at 100 mrem/yr (100,000 μrem/yr or 1 mSv/yr) and the occupational limit at 5,000 mrem/yr (5,000,000 μrem/yr or 50 mSv/yr) for radiation workers.

How many mrem is a chest X-ray?

A standard PA chest X-ray delivers about 2 mrem (2,000 μrem), equivalent to 0.02 mSv or 20 μSv. This is roughly equal to one day of natural background radiation.