How Radiation to be Measured?

Radiation is measured in two units - rads and rems. A rad stands for "radiation absorbed dose" and measures the amount of energy that is actually absorbed per unit mass. A rem stands for "roentgen equivalent man" and is a unit that measures the absorbed dose in human tissue and relates it to the effective damage done to your tissue. It is significant because not all radiation has the same biological effect. The radioactivity of a source is usually measured in how many rads or rems you would receive per hour; a geiger counter normally measures radiation in millirems per hour (mr/hr).

For more details, you could visit radiation protection.