Electric Charge Unit Converter

How to use this calculator

Charge value — Enter your number. The screenshot above shows 1,000 mAh converting to 3,600 coulombs, which is the conversion most people come here for.

From unit — The unit your value is in. The dropdown includes coulombs (C), milliampere-hours (mAh), ampere-hours (Ah), and millicoulombs (mC).

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

The output panel shows all four reference values: coulombs, mAh, Ah, and what’s labeled “MC” in the panel. That label is millicoulombs (mC), not megacoulombs. Megacoulombs are real but rarely useful outside power grid engineering. Everything in the panel is the same charge expressed four ways.

The conversion formula

Charge has two unit families that don’t convert between each other by simple powers of 10. That’s what makes this converter different from the voltage, current, and resistance ones.

Within the coulomb family: powers of 1,000

• 1 coulomb = 1,000 millicoulombs
• 1 coulomb = 1,000,000 microcoulombs

Within the ampere-hour family: powers of 1,000

• 1 Ah = 1,000 mAh
• 1 mAh = 1,000 µAh

Between the two families: a factor of 3,600

The 3,600 factor comes from the definition of both units. A coulomb is 1 ampere flowing for 1 second. An ampere-hour is 1 ampere flowing for 1 hour. 1 hour = 3,600 seconds. So 1 Ah = 1A × 3,600s = 3,600 coulombs.

That’s the one number worth memorizing: 3,600. Everything else follows from it.

Full unit reference table

The mAh is the workhorse unit for anyone dealing with rechargeable batteries. Everything from AirPods (35 mAh) to a phone (3,000–5,000 mAh) to a laptop (50,000–100,000 mAh, usually listed in Wh instead) to a Tesla Model 3 long-range pack (about 240,000 mAh = 240 Ah = 75 kWh at 312V nominal).

Common conversions at a glance

Within coulombs

Within ampere-hours

Cross-family (the important ones)

The cross-family table is the one that matters. Within each family it’s just powers of 1,000, same as every other metric unit. The 3.6 and 3,600 factors are the conversions people actually need to look up.

Battery capacity: why mAh and not coulombs

The coulomb is the SI unit of charge. So why does nobody rate battery capacity in coulombs?

Partly convention, partly practicality.

Battery capacity ratings come from discharge testing: measure how long a battery lasts at a given current, multiply current by time. Current (mA) × time (hours) = charge (mAh). The arithmetic is clean and the result maps directly to the question every user actually cares about: “how long will this run?”

If a device draws 100 mA and the battery is 3,000 mAh, the theoretical runtime is 3,000 / 100 = 30 hours. That calculation takes 2 seconds. In coulombs: 10,800 C / 0.1 A = 108,000 seconds = 30 hours. Same answer, more steps, no practical advantage.

Coulombs matter when the physics matters: electrochemistry, Faraday’s law of electrolysis, capacitor charge/discharge equations. mAh matters when the engineering matters: battery selection, power budgeting, charging circuit design.

Battery charge visualization: what the tool shows

The battery charge visualization in the calculator maps an mAh value against a reference bar that marks the iPhone 15 capacity (3,279 mAh). The screenshot shows 1,000 mAh sitting at about 10% of the scale, which visually anchors it.

Some useful reference points for that visualization:

The laptop and EV rows switch to Wh because at high voltages, watt-hours (capacity × voltage) is more useful than mAh alone for energy comparisons. A 3,000 mAh phone battery at 3.7V holds 11.1 Wh. A 3,000 mAh laptop battery at 11.1V holds 33.3 Wh. Same charge in mAh, three times the energy in Wh. The distinction matters when comparing across battery systems at different voltages.

Real-world examples

Estimating phone charge from a power bank

A 10,000 mAh power bank is used to charge a phone with a 3,800 mAh battery. How many full charges?

Capacitor charge in coulombs

A 100 µF capacitor is charged to 12V. How much charge does it hold?

Electroplating: coulombs determine deposit thickness

Electroplating uses Faraday’s law to relate charge to the amount of material deposited:

m = (Q × M) / (n × F)

Where m is mass deposited, Q is charge in coulombs, M is molar mass of the metal, n is the number of electrons transferred per ion, and F is the Faraday constant (96,485 C/mol).

EV battery capacity in Ah vs coulombs

A 75 kWh EV battery pack at 350V nominal voltage. What’s the capacity in Ah, mAh, and coulombs?

Battery charging time

A 4,000 mAh phone battery is at 20% charge and charging at 25W via USB-C. Assuming 5V charging at 5A (25W = 5V × 5A):

Charge and capacitors: a separate relationship

For capacitors, charge, voltage, and capacitance relate as:

Q = C × V

Where Q is in coulombs, C is in farads, and V is in volts.

This gives a reference table for common capacitor values at common voltages:

The last row is instructive. A 3,000 F supercapacitor at 2.7V holds 8,100 coulombs of charge, which converts to only about 2.25 mAh. A single AA battery holds about 2,500 mAh. Energy density, not charge alone, is what limits supercapacitors as battery replacements.

Charge density and Faraday’s constant

Faraday’s constant (F = 96,485 C/mol) shows up in any electrochemical calculation: plating, electrolysis, fuel cells, lithium-ion battery theory.

It represents the charge carried by one mole of electrons (6.022 × 10²³ electrons, Avogadro’s number). One electron carries 1.602 × 10⁻¹⁹ coulombs, and 6.022 × 10²³ × 1.602 × 10⁻¹⁹ = 96,485 C.

In mAh: 96,485 C / 3.6 = 26,801 mAh per mole of electrons

This is directly useful in battery chemistry. Lithium-ion cathode materials are often rated in mAh/g (specific capacity). LFP (lithium iron phosphate) cathode material has a theoretical capacity of about 170 mAh/g. NMC (nickel manganese cobalt) is about 270 mAh/g. These numbers come from Faraday’s law applied to the atomic weight and electron count of the electrochemical reaction.

The converter handles the mAh-to-coulomb conversion; the chemistry gives you what to do with it.

Where charge unit confusion costs you

Confusing mAh and mA. A battery rated at 3,000 mAh and a device drawing 300 mA are in different units. The runtime is 3,000 mAh / 300 mA = 10 hours. Both are in milliampere-based units, but mAh is charge and mA is current. Dividing them gives hours. This is correct, but it’s tempting to think both are “current” units because they share the “mA” prefix. The “h” in mAh means the time is already baked in.

mAh vs Wh for cross-voltage comparisons. A 10,000 mAh portable charger marketed to charge laptops might be more limited than it sounds. At 3.7V (the cell voltage), 10,000 mAh = 37 Wh. A laptop that needs 65 Wh would barely get a half charge. The mAh rating is technically correct but voltage-dependent. Wh is more honest for cross-device energy comparisons. The converter doesn’t convert to Wh (that requires knowing voltage), but knowing that 1 mAh at 3.7V = 3.7 mWh lets you compute it.

Coulombs in a charging spec without context. Some scientific instruments specify electrode charge limits in coulombs to protect the tissue or material being stimulated. “Maximum charge per phase: 0.5 µC” means every pulse can deliver no more than 0.5 µC. In mAh: 0.5 µC / 3,600,000 µC per mAh = 0.000000139 mAh per pulse. The mAh conversion is useless here; the µC limit is what matters, and the charge-per-phase specification exists precisely because coulombs are the right unit for the physics.

Self-discharge expressed in µAh. A coin cell’s self-discharge is sometimes given in µA. Over time, that current slowly drains the battery. A 250 µA self-discharge current over 1 year = 250 µA × 8,760 hours = 2,190,000 µAh = 2,190 mAh. If the battery has 200 mAh capacity, it’s dead before you even use it. This conversion (µA × hours = µAh, then ÷1,000 to mAh) is the one that catches people specifying long-shelf-life applications.

The coulomb in context

One coulomb sounds abstract. Some physical anchors:

The lightning bolt is the surprising one: 30 kA sounds enormous, but it lasts about 0.2 milliseconds, so the total charge transferred is only about 5–6 coulombs. Less than the charge in a pair of AirPods.

The bottom line

Electric charge has two unit families. Within each, it’s powers of 1,000. Between them, multiply or divide by 3,600.

mAh to coulombs: multiply by 3.6. Coulombs to mAh: divide by 3.6. Ah to coulombs: multiply by 3,600. That’s the complete cross-family conversion.

The converter handles all of it and shows all four units simultaneously, with a battery visualization that anchors abstract numbers against a real device. The mAh-to-coulombs path is the one most people come here for, usually because a battery spec and a physics calculation are in different unit families and they need to get them onto the same footing.