One coulomb is exactly 0.2777777778 milliamp-hours, so converting coulombs to milliamp-hours 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 coulomb is the SI unit of electric charge: one ampere flowing for one second. The milliamp-hour is how every phone, laptop and power-bank battery is rated. One mAh is 3.6 coulombs, because an hour is 3,600 seconds.
Milliamp-hours are charge, not energy. Two batteries both rated 3,000 mAh store different amounts of energy if their voltages differ, which is why power banks advertise mAh at cell voltage and deliver less at USB voltage. Below the calculator there is a step table for the values people look up most, and a second table putting real the total quantity of electricity, including battery capacity figures into milliamp-hours so the number you get has something to be compared against.
The formula
coulombs- The amount you are converting, in coulombs
0.277777777778- The exact number of milliamp-hours in one coulomb
milliamp-hours- The converted result
How it works, step by step
- Enter the value in coulombs.
- It is multiplied by 0.277777777778, the exact factor between the two units.
- The answer is shown in milliamp-hours, with the reverse conversion beneath it.
- Check the reference table if you want a figure of comparable size.
Worked examples
Phone battery, 4000 mAh: 1.44e+04 C in milliamp-hours
Phone battery, 4000 mAh comes to about 1.44e+04 C. Multiplying by the factor: 1.44e+04 × 0.277778 = 4000 mAh. Dividing the answer back by 0.277778 returns the figure you started with, which is the quickest way to check you have the factor the right way up.
Camera flash capacitor: 0.05 C in milliamp-hours
At 0.05 C (camera flash capacitor), the same quantity in milliamp-hours is 0.05 × 0.277778 = 0.0138889 mAh. One coulomb is 0.277778 milliamp-hours, so the numbers shrink as expected.
How to read your score
Frequently asked questions
How many milliamp-hours are in one coulomb?
Exactly 0.277777777778. 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 coulombs to milliamp-hours?
milliamp-hours = coulombs × 0.277777777778. Reversed, coulombs = milliamp-hours ÷ 0.277777777778, which is the same as multiplying by 3.6.
Which is the bigger unit, the coulomb or the milliamp-hour?
The milliamp-hour. One coulomb is only 0.277778 of a milliamp-hour, so it takes 3.6 coulombs to make one milliamp-hour.
What does this quantity actually measure?
Both units measure the total quantity of electricity, including battery capacity. 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 coulomb?
The coulomb is the SI unit of electric charge: one ampere flowing for one second.
What is a milliamp-hour?
The milliamp-hour is how every phone, laptop and power-bank battery is rated. One mAh is 3.6 coulombs, because an hour is 3,600 seconds.
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.
Coulombs to milliamp-hours reference tables
| Coulombs | Milliamp-Hours |
|---|---|
| 0.5 C | 0.138889 mAh |
| 1 C | 0.277778 mAh |
| 2 C | 0.555556 mAh |
| 3 C | 0.833333 mAh |
| 5 C | 1.38889 mAh |
| 10 C | 2.77778 mAh |
| 20 C | 5.55556 mAh |
| 25 C | 6.94444 mAh |
| 50 C | 13.8889 mAh |
| 75 C | 20.8333 mAh |
| 100 C | 27.7778 mAh |
| 250 C | 69.4444 mAh |
| 500 C | 138.889 mAh |
| 1000 C | 277.778 mAh |
| 5000 C | 1388.89 mAh |
Exact factor: 1 coulomb = 0.277777777778 milliamp-hours.
| Quantity | C | mAh |
|---|---|---|
| AA alkaline cell | 9000 C | 2500 mAh |
| Phone battery, 4000 mAh | 1.44e+04 C | 4000 mAh |
| Laptop battery, 60 Wh at 11.1 V | 1.946e+04 C | 5405 mAh |
| Car battery, 60 Ah | 2.16e+05 C | 6e+04 mAh |
| Camera flash capacitor | 0.05 C | 0.01389 mAh |
| Lightning strike | 15 C | 4.167 mAh |
Published reference values, converted with the same factor this page uses.