500 mA is equal to 0.5 amps. The term “mA” denotes milliamp. In the metric system, amp (A) or ampere is the unit measurement for electric current.
To make this calculation, one has to know the conversion equivalents between these two units. The relationship states that 1 amp is equal to 1 milliamp divided by 1000 milliamps per amp, or A = mA/1000. From this relationship, one can substitute 500 for mA, or 500/1000 that also is 0.5. This is equal to the number of amps.
Converting from amps to milliamps, one can use the equation milliamp = 1000 milliamps per amp x amp, or mA = 1000 x A. If one substitutes 0.5 amp for A into this equation, one finds that mA= 1000 x 0.5 = 500.