Current Converter (A, mA, µA, biot)

Understanding the electric current converter — concept and principle

Electric current is the rate at which charge flows, measured in amperes (A). Electronics datasheets give values in milliamperes or microamperes, power systems in amperes or kiloamperes, and older physics texts sometimes in the CGS unit called the biot or abampere. This converter switches a value between A, mA, µA, kA and biot.

How it is calculated

• 1 mA = 10⁻³ A
• 1 µA = 10⁻⁶ A
• 1 kA = 10³ A
• 1 biot (abampere) = 10 A

result = value × (amperes per "from" unit) ÷ (amperes per "to" unit). SI prefixes are exact, so conversions are exact apart from display rounding.

The principle

One ampere is one coulomb of charge passing a point each second. Since 2019 the SI defines the ampere by fixing the elementary charge at exactly 1.602176634 × 10⁻¹⁹ C, so one ampere corresponds to about 6.24 × 10¹⁸ electrons per second. The biot belongs to the older electromagnetic CGS system, where current was defined through the force between wires; its size works out to exactly 10 A.

Worked example

Default: 1 mA to A.

1. 1 mA = 1 × 10⁻³ A.
2. So the result is 0.001 A.
3. The same current is 1,000 µA, 0.000001 kA and 0.0001 biot (0.001 ÷ 10).

How to read the result

Typical magnitudes help you check a figure: a quartz watch draws around a microampere, an indicator LED often runs at a few to 20 mA, a USB 2.0 port supplies up to 500 mA, phone chargers deliver about 1–3 A, and household appliances draw several amperes. Battery capacity in mAh divided by load current in mA gives an approximate runtime in hours: a 2,000 mAh cell at 100 mA lasts roughly 20 hours.

Common mistakes

• Confusing mA (milliampere) with MA (megaampere), or mA with mAh, which is charge, not current.
• Dropping a factor of 1,000 when moving from µA to A in battery-life estimates.
• Assuming a charger's rated current is always delivered; the device decides how much it draws.
• Connecting an ammeter in parallel; current must be measured in series, and a parallel connection can blow the meter's fuse.

FAQ

Frequently asked questions

How many mA are in 1 A?

1,000 mA.

Is mAh a unit of current?

No; it is charge (current × time). 1,000 mAh is 1 Ah, or 3,600 coulombs.

What is an abampere?

The CGS electromagnetic unit of current, also called the biot, equal to 10 A.

Sources: BIPM, The International System of Units (SI Brochure), 9th edition · NIST Special Publication 811 (2008), Appendix B