Free tool
Amps to Milliamps Calculator
Milliamps are amps times 1,000. The mistakes are in the small decimals — 0.004 A and 0.04 A are a factor of ten apart, and one of them trips a GFCI.
mA = A × 1,000
Milliamps = amps × 1,000. 0.5 A is 500 mA, 0.02 A is 20 mA, and 1.5 A is 1,500 mA. For watts, multiply the amps by the voltage. Going the other way is the milliamps to amps calculator; for amp-hours of battery capacity, the same factor of 1,000 turns Ah into mAh.
The current
For amp-hours (Ah), the step is the same — 2.5 Ah is 2,500 mAh — but the result is a battery capacity, not a current.
The answer
Milliamps
500 mA
mA = A × 1,000 → 0.5 × 1,000
Against USB at 5 V
500 mA is within a standard USB 2.0 port's 500 mA. The port or charger sets the ceiling; the device decides what it actually draws.
Against a GFCI
A Class A GFCI trips when current leaking to ground reaches 6 mA and does not trip below 4 mA. 500 mA is at or above that level — ordinary as a device's working current, enough to trip a Class A GFCI if it were leaking to ground.
Informational use only, please verify before you rely on it
This reproduces the unit conversion mA = A × 1,000, with an optional W = A × V step. It is a preparation aid, not a determination. It does not size conductors or overcurrent protection, and it does not decide where ground-fault protection is required. Confirm against the equipment nameplates and applicable codes.
This tool is provided for general informational and educational purposes only. Its output is an illustrative estimate generated from the values you enter and from general assumptions that will not match every deal, market, lender, or homeowner. It is not tax, legal, accounting, financial, or professional advice, and it is not a quote, an offer, a credit decision, or a guarantee of pricing, approval, timing, savings, or eligibility.
You are solely responsible for independently confirming all information presented here including any figures, rates, fees, margins, timelines, tax treatment, and federal, state, local, or utility incentives, with the applicable lender, authority having jurisdiction, and your own qualified tax, legal, and financial advisors before acting on it, relying on it, or presenting it to a homeowner or any third party. Incentive programs, lender terms, and permitting requirements change frequently and vary by jurisdiction.
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A to mA conversion table
| Amps (A) | Milliamps (mA) |
|---|---|
| 0.001 A | 1 mA |
| 0.004 A | 4 mA |
| 0.006 A | 6 mA |
| 0.01 A | 10 mA |
| 0.02 A | 20 mA |
| 0.04 A | 40 mA |
| 0.1 A | 100 mA |
| 0.25 A | 250 mA |
| 0.5 A | 500 mA |
| 0.9 A | 900 mA |
| 1 A | 1,000 mA |
| 1.5 A | 1,500 mA |
| 3 A | 3,000 mA |
When a figure in amps needs to be read in milliamps
Meter readings. A multimeter on its amps range may show a reading such as 0.012 A; the same current is 12 mA. Many meters have a separate, lower-rated milliamp input, so switching to it for a small current is common — and measuring a full appliance current through it is how its fuse gets blown.
USB and charging. Port limits are written in milliamps — 500 mA for USB 2.0, 900 mA for USB 3.x — while chargers often state their output in amps. A charger rated 5 V ⎓ 2.4 A supplies up to 2,400 mA. The laptop watts post covers why a charger's rating is a ceiling rather than what the device draws.
Standby and leakage. A device on standby may draw 0.01 A or less — 10 mA — and leakage current to ground is measured in milliamps because that is the scale at which shock protection works. A Class A GFCI trips at 6 mA, and where it is required in a kitchen, bathroom, laundry or garage is set by the NEC and local amendments; the refrigerator amps post covers why a GFCI that keeps tripping on an appliance is reporting leakage.
Resistive circuits. 12 V across a 1 kΩ resistor is 0.012 A, or 12 mA. The Ohm's law calculator works in milliamps and kilohms directly.
Frequently Asked Questions
How do you convert amps to milliamps?+
Multiply by 1,000: mA = A × 1,000. 0.5 A is 500 mA, 0.02 A is 20 mA and 1.5 A is 1,500 mA. Moving the decimal point three places to the right does the same thing.
How many milliamps is 1 amp?+
1,000 milliamps. "Milli" means one-thousandth, so one amp is a thousand milliamps.
What is 0.04 amps in milliamps?+
40 mA (0.04 × 1,000). Small decimals are where conversions go wrong: 0.004 A is 4 mA, and 0.0004 A is 0.4 mA. Counting the places after the decimal point is the safest check.
How many milliamps can a USB port supply?+
At 5 V, a USB 2.0 port is specified for 500 mA and a USB 3.x port for 900 mA. USB Battery Charging 1.2 allows up to 1,500 mA, and USB Type-C advertises 1,500 or 3,000 mA at 5 V. Higher USB-C power comes from negotiating a higher voltage through USB Power Delivery rather than more current at 5 V.
Why are some currents written in milliamps instead of amps?+
Because the numbers are small enough that amps would need awkward decimals. Sensor loops, LEDs, standby draw, leakage current and ground-fault thresholds are all naturally stated in milliamps; circuits and appliances are stated in amps.
Is a current in milliamps dangerous?+
It can be, which is why shock protection is specified in milliamps. A Class A GFCI is designed to trip when current leaking to ground reaches 6 mA and not to trip below 4 mA. The working current of the appliance plugged into the same outlet can be many amps; it is current going somewhere it should not that the GFCI measures.
Is this a determination?+
No. It reproduces the unit conversion mA = A × 1,000 and the power relationship W = A × V as a preparation aid. It does not size conductors or overcurrent protection and does not decide whether ground-fault protection is required at a location.
Related resources
Milliamps to Amps Calculator
The reverse step, with a mAh mode for battery capacity.
Learn more →Ohm's Law Calculator
Any two of volts, amps, ohms and watts, in mA or kΩ too.
Learn more →mAh to Wh Calculator
Battery capacity in milliamp-hours turned into watt-hours.
Learn more →Amps to Watts Calculator
Watts from current on DC, single-phase and three-phase circuits.
Learn more →Small numbers, read correctly
Seamless Home runs the design, permit and interconnection layer for the partners it works with — where a rating in milliamps, amps or watts gets read as the figure it actually is. Coverage is confirmed per service area rather than promised as blanket availability.
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