Current Converter
Convert between electrical current units: nanoamperes, microamperes, milliamperes, amperes, kiloamperes, and more. Includes Ohm's Law calculator.
Current Converter
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Formula: I = V / R (Ohm's Law) | Unit Conversion via Ampere base
Worked example โ 20 mA = 0.02 A | Power = 66 mW
Formula
I = V / R (Ohm's Law) | Unit Conversion via Ampere base
Current units convert through the ampere (SI base unit). Multiply by the source unit's ampere factor, then divide by the target's factor. Ohm's Law (I = V/R) relates current to voltage and resistance: current in amperes equals voltage in volts divided by resistance in ohms.
Worked Examples
Example 1: LED Circuit Current
Problem:An LED circuit draws 20 mA. Convert to amperes and calculate power at 3.3V.
Solution:Convert: 20 mA x 0.001 A/mA = 0.02 A Power = V x I = 3.3V x 0.02A = 0.066W = 66 mW The LED consumes 20 milliamperes = 0.02 amperes and dissipates 66 milliwatts.
Result:20 mA = 0.02 A | Power = 66 mW
Example 2: Industrial Motor Current
Problem:A motor draws 2.5 kA. Express in amperes and milliamperes.
Solution:To amperes: 2.5 kA x 1000 A/kA = 2,500 A To milliamperes: 2,500 A x 1000 mA/A = 2,500,000 mA Or directly: 2.5 kA x 1,000,000 mA/kA = 2,500,000 mA
Result:2.5 kA = 2,500 A = 2,500,000 mA
Frequently Asked Questions
What is electric current and what are its units?
Electric current is the flow of electric charge through a conductor, measured in amperes (A). One ampere equals one coulomb of charge passing a point per second. Current is one of the seven SI base units. Common subunits include milliamperes (mA, one thousandth of an ampere) used for small electronics, and microamperes (uA, one millionth) used in sensor circuits. Kiloamperes (kA) measure large industrial currents like those in arc furnaces.
How do I convert between different current units?
All current units relate to the ampere by powers of 10. To convert, multiply the value by the source unit's ampere equivalent, then divide by the target unit's equivalent. For example, to convert 500 mA to amperes: 500 x 0.001 = 0.5 A. To convert 2.5 A to milliamperes: 2.5 / 0.001 = 2,500 mA. The metric prefixes follow standard SI scaling: nano (1e-9), micro (1e-6), milli (1e-3), kilo (1e3), mega (1e6).
What is the relationship between current, voltage, and resistance?
Ohm's Law states that current (I) equals voltage (V) divided by resistance (R): I = V/R. This fundamental relationship governs all resistive circuits. If you know any two values, you can calculate the third. For example, a 12V battery connected to a 100-ohm resistor produces 0.12 A (120 mA) of current. Power dissipated is P = V x I = 12 x 0.12 = 1.44 watts.
What are abamperes and statamperes?
Abamperes and statamperes are units from the CGS (centimeter-gram-second) electromagnetic system, largely replaced by SI units. One abampere (also called a biot) equals 10 amperes and was defined based on the force between parallel conductors in the CGS-EMU system. One statampere equals approximately 3.336 x 10^-10 amperes, from the CGS-ESU system based on electrostatic force. These units are now mainly encountered in older physics literature and theoretical calculations.
What is the difference between AC and DC current?
Direct current flows in one direction at a steady magnitude, as from a battery or a DC supply. Alternating current reverses direction periodically, following a sine wave in mains supply. AC is normally quoted as an RMS value, the equivalent DC current that would deliver the same heating in a resistor. For a sinusoid, the RMS value equals the peak divided by the square root of 2, so a 10 A peak is about 7.07 A RMS. Meters and ratings almost always mean RMS unless peak is stated.
How is the ampere defined in the SI system?
Since the 2019 revision of the SI, the ampere is defined by fixing the numerical value of the elementary charge at 1.602176634 times 10 to the power of -19 coulombs, with the second defined separately from the caesium transition. One ampere is therefore one coulomb of charge per second expressed through that fixed constant. The previous definition used the force between two infinite parallel conductors. The change does not alter the practical size of the ampere, only how it is realised in metrology laboratories.
How do I find current from power and voltage?
For a DC circuit, current equals power divided by voltage, so a 1,200 watt load on a 120 volt supply draws 10 amperes. For single-phase AC you must also divide by the power factor, because real power is voltage times current times power factor. A 1,200 watt motor at 120 volts with a power factor of 0.8 draws 12.5 amperes, not 10. Ignoring power factor understates the current a conductor or breaker actually has to carry.
What is current density and how does it differ from current?
Current density is current divided by the cross-sectional area of the conductor, usually expressed in amperes per square millimetre or per square metre. Two conductors can carry the same current at very different densities if their gauges differ. Density is what determines heating and voltage drop per unit length, so conductor sizing rules, printed circuit board trace width tables and busbar ratings are all effectively current density limits rather than current limits.
What does a battery rating in milliampere-hours actually measure?
Milliampere-hours measure charge capacity, not current. A rating of 2,000 mAh means the cell can in principle supply 2,000 milliamperes for one hour, 500 milliamperes for four hours, or 100 milliamperes for twenty. Divide the capacity by your average draw in the same unit to estimate runtime. Real capacity falls at high discharge rates, at low temperature and as the cell ages, so treat the arithmetic as an upper bound rather than a specification.
When would I work in microamperes rather than milliamperes?
Microamperes suit currents small enough that milliamperes would force awkward leading zeros: sleep-mode consumption in a microcontroller, leakage through a reverse-biased junction, photodiode and sensor output, and input bias current in an operational amplifier. One milliampere is 1,000 microamperes. Choosing the prefix that keeps the mantissa between about 1 and 999 makes datasheet comparisons far easier and reduces the chance of a thousand-fold slip when logging measurements.
References
Reviewed for accuracy by Manoj Kumar, Mathematics Educator ยท Editorial policy
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