milliamperes

Milliamperes (mA) are a unit of electric current in the International System of Units (SI). One milliamperes equals one thousandth of an ampere (1 mA = 0.001 A). The milliampere is a common unit for expressing small currents in electronics and electrical engineering.

In practice, milliamperes are used to describe currents in circuits, such as the current through LEDs, transistors, sensors, and other components. Device datasheets often specify forward currents, input currents, or load currents in milliamperes. The value needed for a given circuit depends on the components and supply voltage; power can be estimated with P = V × I, so a 5-volt supply at 20 mA draws about 0.1 watts.

Measuring milliamperes typically involves an ammeter or a multimeter set to the mA range. When measuring, the circuit is usually opened and the meter inserted in series with the path of current. Many multimeters use a dedicated mA input with a internal fuse, while higher currents may use a separate 10 A input. For very small currents, microamperes may be more appropriate and require higher-impedance measurement techniques.

Related units include the ampere (A) and the microampere (µA). The relationship is 1 A = 1000 mA and 1 mA = 1000 µA. It is important not to confuse milliamperes with milliampere-hours (mAh), a unit of stored charge or battery capacity rather than current.

Typical applications vary widely, from LED indicators (often 5–20 mA) to microcontroller I/O and sensor circuits (ranging from microamps to a few milliamps).