One ampere is exactly 1000 milliamps, so converting amperes to milliamps is a single multiplication. Enter any figure and the result appears as you type — the arithmetic runs in your browser, so nothing is sent anywhere.
The milliamp is the unit almost every consumer specification uses: phone chargers, LEDs and fuses are all rated in mA. The ampere is the SI base unit of electric current, defined since 2019 by fixing the elementary charge at 1.602176634 x 10^-19 coulombs.
Two tables follow: rounded steps for quick lookup, and a set of real reference quantities converted into milliamps, which is usually more useful than the bare number.
The formula
amperes- The amount you are converting, in amperes
1000- The exact number of milliamps in one ampere
milliamps- The converted result
How it works, step by step
- Enter the value in amperes.
- It is multiplied by 1000, the exact factor between the two units.
- The answer is shown in milliamps, with the reverse conversion beneath it.
- Check the reference table if you want a figure of comparable size.
Worked examples
MIG welder at full output: 250 A in milliamps
Take mig welder at full output, roughly 250 A. The conversion is a single multiplication — 250 × 1000 — giving 250,000 mA. Because the relationship is proportional, doubling the input doubles the answer to 500,000 mA.
Car starter motor: 300 A in milliamps
At 300 A (car starter motor), the same quantity in milliamps is 300 × 1000 = 300,000 mA. One ampere is 1000 milliamps, so the numbers grow as expected.
How to read your score
Frequently asked questions
How many milliamps are in one ampere?
Exactly 1000. Every figure on this page is that one number multiplied by your input, so the only rounding is at the display step.
What is the formula to convert amperes to milliamps?
milliamps = amperes × 1000. Reversed, amperes = milliamps ÷ 1000, which is the same as multiplying by 0.001.
Which is the bigger unit, the ampere or the milliamp?
The ampere. One ampere equals 1000 milliamps.
What does this quantity actually measure?
Both units measure how much charge flows past a point each second. That is why a single factor is enough: there is no temperature offset and no material property involved, unlike conversions that cross between different quantities.
What is a ampere?
The ampere is the SI base unit of electric current, defined since 2019 by fixing the elementary charge at 1.602176634 x 10^-19 coulombs.
What is a milliamp?
The milliamp is the unit almost every consumer specification uses: phone chargers, LEDs and fuses are all rated in mA.
Why does my answer differ from another converter?
Almost always because the other tool rounded the factor before multiplying. This page keeps full double precision through the calculation and rounds only for display, and it prints the factor it used so you can see where any difference came from.
Amperes to milliamps reference tables
| Amperes | Milliamps |
|---|---|
| 0.5 A | 500 mA |
| 1 A | 1000 mA |
| 2 A | 2000 mA |
| 3 A | 3000 mA |
| 5 A | 5000 mA |
| 10 A | 10,000 mA |
| 20 A | 20,000 mA |
| 25 A | 25,000 mA |
| 50 A | 50,000 mA |
| 75 A | 75,000 mA |
| 100 A | 100,000 mA |
| 250 A | 250,000 mA |
| 500 A | 500,000 mA |
| 1000 A | 1e+06 mA |
| 5000 A | 5e+06 mA |
Exact factor: 1 ampere = 1000 milliamps.
| Quantity | A | mA |
|---|---|---|
| LED indicator | 0.02 A | 20 mA |
| Phone fast charger | 3 A | 3000 mA |
| Domestic ring-main fuse (UK) | 32 A | 3.2e+04 mA |
| Car starter motor | 300 A | 3e+05 mA |
| MIG welder at full output | 250 A | 2.5e+05 mA |
| Microcontroller sleep mode | 5e-06 A | 0.005 mA |
Published reference values, converted with the same factor this page uses.