Electric Current Unit Converter

How to use this calculator

Current value — Type your number. The converter handles everything from fractional microamperes to thousands of kiloamperes.

From unit — The unit your value is currently in: Ampere, Milliampere, Microampere, or Kiloampere.

To unit — The unit you want the primary result in.

The output panel shows the converted value prominently, with all four units displayed below it simultaneously: A, mA, µA (shown as MA in the panel), and kA. One input, four outputs, no repeat conversions.

The conversion formula

Current units are metric and all powers of 1,000. The ampere is the SI base unit.

1 kiloampere = 1,000 amperes 1 ampere = 1,000 milliamperes 1 milliampere = 1,000 microamperes 1 ampere = 1,000,000 microamperes

Going from a larger unit to a smaller one: multiply by 1,000 per step. Going up the scale: divide by 1,000 per step.

µA to mA: divide by 1,000. mA to A: divide by 1,000. A to kA: divide by 1,000. Same chain, same rule, every time.

Full unit reference table

The span from µA to kA is 9 orders of magnitude. A pacemaker runs on roughly 10 µA average current. A Tesla Model 3 motor draws up to about 1,500A (1.5 kA) at peak acceleration. The same physical quantity, the same unit family, just nine decades apart.

Common conversions at a glance

The pair you’ll use most often in low-power electronics: mA to A (÷1,000) and A to mA (×1,000). Datasheets for microcontrollers list supply current in mA; power budgets are usually calculated in watts (V × A), so converting mA to A is a constant background task.

Current in the real world: a reference scale

This is the table the calculator’s “real-world reference scale” feature points toward. These are approximate values for familiar things.

The table reveals something useful: human-scale electronics (phones, computers, household appliances) sits almost entirely in the 1 mA to 20 A range. Go below 1 mA and you’re in sensor/sleep territory. Go above 20 A and you’re in motor, EV, or industrial territory.

Ohm’s law: current, voltage, and resistance together

Current doesn’t exist in isolation in a circuit. It’s linked to voltage and resistance by Ohm’s law:

V = I × R (voltage = current × resistance)

Which rearranges to:

I = V / R (current = voltage / resistance) R = V / I (resistance = voltage / current)

Converting current units matters here because Ohm’s law requires consistent units throughout. If voltage is in volts and resistance is in ohms, current must be in amperes to get a correct result.

The Ohm’s law result is always in amperes when V is in volts and R is in ohms. Then you convert to whatever unit is useful: milliamperes for a datasheet comparison, microamperes if you’re looking at battery life.

Real-world examples

LED current limiting resistor

An LED with a forward voltage of 2.1V is powered from a 5V supply. Maximum LED current is 20 mA. What resistor limits the current correctly?

Microcontroller battery life estimation

An ESP32 module draws 240 mA during Wi-Fi transmission, 20 mA in light sleep, and 10 µA in deep sleep. The device transmits for 0.5 seconds every 10 minutes, spends 5 seconds in light sleep after transmission, and is in deep sleep the rest of the time.

Fuse selection

A 12V DC motor draws 8A at full load and has a startup surge of about 3× running current (24A for a brief inrush). What fuse is appropriate?

Charging current for a lithium battery

A 3,000 mAh lithium-ion battery should be charged at 0.5C rate (C is the capacity, so 0.5C = 0.5 × capacity in A).

Short circuit fault current

An electrical panel in a commercial building is rated for a maximum short-circuit current of 25 kA (the “AIC rating,” ampere interrupting capacity). A circuit breaker must be rated to interrupt at least this current safely.

Current and power: the other fundamental relationship

Power is current × voltage:

P (watts) = I (amperes) × V (volts)

Converting current units affects every power calculation. The table below shows how current and voltage combine to produce power across common scenarios.

The milliampere-to-ampere conversion is invisible but constant in this table. A 20 mA LED current in the power formula requires 0.020 A, not 20. Leaving it in milliamperes and multiplying by the voltage gives 66 mW only if you remember that the result is in milliwatts (mV × mA = µW, mA × V = mW). Mixing units in power calculations without converting first produces wrong answers that can be hard to spot because the arithmetic is still internally consistent, just in unexpected units.

Current density: when amperes aren’t enough

Amperes measure total current through a conductor. Current density measures how much current flows per unit area, and it’s what determines whether a wire or trace overheats.

J = I / A (current density = current / cross-sectional area)

The unit is A/m² or more practically A/mm² for copper conductors.

A standard 0.2mm² wire (28 AWG) has a continuous current capacity of about 0.5 A at 3 A/mm² (conservative) to about 1A at 5 A/mm². In milliamperes: 500 mA to 1,000 mA.

This matters when you convert between current units and discover that 3,000 mA (3 A) flowing through a PCB trace is not automatically safe just because “3” sounds small. At 3 A/mm² on a 0.1mm² trace, you’re at 30 A/mm², which is above the continuous limit and will heat the trace significantly.

AC current: RMS and peak

Just like AC voltage, AC current has a peak value and an RMS (root mean square) value.

For a sinusoidal current:

Ipeak = Irms × √2 ≈ Irms × 1.4142 Irms = Ipeak / √2 ≈ Ipeak × 0.7071

A household circuit protected by a 15A breaker is rated at 15A RMS. The actual peak current is 15 × 1.4142 ≈ 21.2 A peak.

The converter converts between unit scales (A, mA, µA, kA). The RMS-to-peak conversion is separate and requires the √2 factor. If a datasheet specifies peak current and your circuit protection is rated in RMS (as all fuses and breakers are), you need both conversions.

Fuses and circuit breakers trip on RMS current (they respond to heating, which is I²R and relates to RMS). Semiconductor datasheets often specify peak current limits (the maximum instantaneous current before the device is damaged). Always check which type a given specification is using.

Where current unit confusion causes problems

mA vs A in Arduino code. Many Arduino sensor libraries report current in milliamperes as a float. Feeding that number directly into a power calculation (P = I × V) gives you milliwatts when you expect watts. The code runs, the numbers look plausible (66 instead of 0.066), and the error goes unnoticed until someone actually measures the power consumption.

µA spec on a “low-power” part that isn’t. A datasheet lists “sleep current: 50 µA.” Sounds tiny. Over a year on a 1,000 mAh coin cell: 50 µA × 8,760 hours = 438 mAh consumed in sleep alone. The coin cell is dead in about 2 years with zero active-mode operation included. Whether that’s acceptable depends on the application, but converting µA to annual mAh makes the constraint concrete.

Fuse ratings in mixed units. A fuse rated “250 mA” and a circuit drawing “0.3 A” — does the fuse blow? 250 mA = 0.25 A. The 0.3 A circuit exceeds the fuse rating. The fuse blows. This comparison is only obvious if both values are in the same unit first.

kA ratings on breakers vs fault current in A. An engineer specifying a breaker checks that the breaker’s AIC rating exceeds the available fault current. If the fault current calculation produces 18,500 A and the breaker is rated “22 kA,” is it sufficient? 22 kA = 22,000 A. Yes, it’s sufficient. But mixing kA and A in the comparison without converting first is how mistakes happen in panel design.

The ampere: what it actually measures

The ampere measures charge flow over time: 1 ampere = 1 coulomb per second. A coulomb is approximately 6.24 × 10¹⁸ electrons. So 1 mA is about 6.24 × 10¹⁵ electrons per second, and 1 µA is 6.24 × 10¹² electrons per second.

These numbers are too large to be intuitive, but the coulomb connection matters for battery calculations. Battery capacity is often measured in milliampere-hours (mAh), which is just charge (current × time).

Charge (mAh) = Current (mA) × Time (hours)

A 2,000 mAh battery can supply:

• 2,000 mA for 1 hour
• 200 mA for 10 hours
• 20 mA for 100 hours
• 1 mA for 2,000 hours (~83 days)

In ampere-hours: 2,000 mAh = 2 Ah. In coulombs: 2 Ah × 3,600 seconds/hour = 7,200 coulombs. In electrons: 7,200 × 6.24 × 10¹⁸ ≈ 4.5 × 10²² electrons.

The mAh unit is more useful for battery comparisons than any of those. But the conversion between mA, A, and kA is the step you run constantly when matching battery capacity to a device’s supply current spec.

The bottom line

Current unit conversions are powers of 1,000. A to mA: multiply by 1,000. mA to µA: multiply by 1,000. A to kA: divide by 1,000. The converter does this instantly and shows all four units simultaneously.

The practical traps: mA vs A in Ohm’s law and power calculations (divide by 1,000 before plugging in), µA sleep currents that look negligible until you multiply by hours, and kA fault current ratings that look small until you convert them to amperes and compare against calculated fault current.

The reference scale table in the calculator is worth bookmarking. Whether 100 mA is “a lot” depends entirely on context. For an LED it’s five times the rated current. For a USB device it’s well within spec. For a motor it’s probably stall current of a tiny motor. The number alone tells you nothing; the application range tells you everything.