Electric Charge Unit Converter
Convert between any pair of electric-charge units — coulombs, ampere-hours, milliampere-hours, the elementary charge, statcoulombs, faradays — using factors verified against NIST, BIPM, and the CODATA value of the elementary charge. Type a value and the result updates instantly.
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What is electric charge, and why so many units?
Electric charge is a fundamental property of matter that determines how a particle responds to electromagnetic fields. In SI units, the coherent unit of charge is the coulomb (C), defined since the 2019 redefinition of the SI as the charge transported by a current of one ampere flowing for one second — but anchored to a fixed value of the elementary charge: e = 1.602 176 634 × 10⁻¹⁹ C, exactly. That single defining constant ties together every unit on this page, from the picocoulomb on the gate of a transistor to the kilo-ampere-hours stored in an electric-vehicle battery pack.
Charge spans an enormous range. A single electron carries 1.6 × 10⁻¹⁹ C. A typical lightning bolt transfers about 15 C in a millisecond. A 5,000 mAh smartphone battery delivers 18,000 C between full charge and empty. A copper-refining cell can pass tens of millions of coulombs every day. To keep numbers readable across that range, engineers and physicists use SI prefixes (mC, μC, nC, pC) for small charges, the ampere-hour family (Ah, mAh) for batteries — because manufacturers specify capacity in current × time — and a few legacy units like the statcoulomb (CGS) and the faraday (one mole of electron-charges) that survive in chemistry, electroplating, and older physics texts.
The charge units, explained
Coulomb (C) and its decimal multiples
The coulomb is the SI unit of electric charge: 1 C is the charge carried by a steady current of 1 A for 1 second. It is large for many electronics applications, so the millicoulomb (mC, 10⁻³ C), microcoulomb (μC, 10⁻⁶ C), nanocoulomb (nC, 10⁻⁹ C) and picocoulomb (pC, 10⁻¹² C) are standard. Capacitor charge, ESD events, and piezoelectric outputs are usually quoted in nC or pC; charge stored in supercapacitors lands in the kC range.
Elementary charge (e) — the modern SI anchor
Since 20 May 2019, the elementary charge is defined as exactly e = 1.602 176 634 × 10⁻¹⁹ C. One coulomb therefore corresponds to about 6.241 509 × 10¹⁸ elementary charges. Particle physicists, semiconductor engineers, and chemists routinely report charge as a count of e (e.g. "a single-electron transistor switches one e per gate cycle").
Ampere-hour (Ah) and milliampere-hour (mAh) — the battery world
Battery capacity is technically charge: one ampere-hour is the charge transferred by 1 A flowing for 1 hour, so 1 Ah = 3,600 C and 1 mAh = 3.6 C. Manufacturers prefer Ah/mAh because they map directly onto run-time at a known load. A 5,000 mAh smartphone battery can supply 1 A for 5 hours, or 100 mA for 50 hours, before discharge — at the nominal voltage.
Statcoulomb (statC) — the CGS-Gaussian survivor
In the older centimetre-gram-second (Gaussian) system used in much of theoretical physics until the 1980s, charge is measured in statcoulombs (also called esu or franklins). The conversion is 1 statC ≈ 3.335 640 95 × 10⁻¹⁰ C. You will mostly meet it in classical electrodynamics textbooks, where Maxwell's equations look slightly cleaner without the 4π factors of SI.
Faraday (F) — the chemist's charge unit
One faraday is the charge of one mole of electrons: F = N_A × e ≈ 96,485.332 12 C. It quantifies how much charge is needed to electrolyse one mole of a singly-ionised species — central to Faraday's laws of electrolysis, electroplating, and battery coulombic-efficiency calculations. Watch out for the symbol clash: the same letter F is used for the farad (the SI unit of capacitance), which is unrelated.
Real-world applications and which unit to expect
- Smartphone and laptop batteries: Smartphone batteries are quoted in mAh (typical 3,000–5,500 mAh) and laptops in Wh (which equals V × Ah). A 5,000 mAh, 3.85 V battery stores 5 × 3.85 = 19.25 Wh, or 18,000 C of charge.
- Electric vehicles: EV pack capacity is usually given in kWh (energy), but the charge is also Ah-scale: a 75 kWh / 360 V Tesla pack stores about 208 Ah, or 750,000 C of charge.
- Capacitor discharge: A 1,000 μF capacitor charged to 12 V holds Q = CV = 12 mC. Camera flash capacitors and defibrillators store tens to hundreds of mC and dump them in milliseconds.
- Electronics — ESD and gate charge: An electrostatic discharge from a person can be 100 nC at several kV. MOSFET gate charge data sheets list nC values that determine switching losses.
- Electroplating and electrolysis: Faraday's laws predict the metal deposited from current × time. Plating 1 mole of copper (Cu²⁺ → Cu) needs 2 F = 192,970 C, regardless of voltage.
- Lightning: A typical cloud-to-ground stroke transfers 5–20 C in under a millisecond. The peak current is huge (≈30 kA), but total charge is moderate.
- Particle physics: Detectors count charge in units of e. The LHC's beam delivers ~10¹¹ protons per bunch, each with charge +1 e, giving total bunch charge near 16 nC.
How much is 1 unit of each in coulombs?
| Unit | Value in coulombs (C) |
|---|---|
| 1 C (Coulomb) | 1 Pa |
| 1 mC (Millicoulomb) | 0.001 Pa |
| 1 μC (Microcoulomb) | 0.000001 Pa |
| 1 nC (Nanocoulomb) | 0.000000001 Pa |
| 1 pC (Picocoulomb) | 1e-12 Pa |
| 1 e (Elementary charge) | 1.602176634e-19 Pa |
| 1 Ah (Ampere-hour) | 3600 Pa |
| 1 mAh (Milliampere-hour) | 3.6 Pa |
| 1 statC (Statcoulomb (CGS)) | 3.3356409519815204e-10 Pa |
| 1 F (Faraday (charge of 1 mole of electrons)) | 96485.33212 Pa |
Frequently asked questions about electric charge
How do I convert between any two charge units?
Multiply by the source unit's coulomb-factor and divide by the target's. Example: 4,500 mAh to coulombs → 4,500 × 3.6 = 16,200 C. The converter above does this in real time.
What's the difference between Ah and Wh?
Ampere-hours measure charge (current × time). Watt-hours measure energy (power × time = voltage × current × time). They are related by the cell voltage: Wh = Ah × V. A 5,000 mAh battery at 3.7 V stores 18.5 Wh; at 12 V it would be 60 Wh. Two batteries with the same Ah at different voltages do not store the same energy.
How many electrons are in 1 coulomb?
Since the elementary charge is defined as exactly 1.602 176 634 × 10⁻¹⁹ C, one coulomb contains 1 / e ≈ 6.241 509 × 10¹⁸ electrons (or any other particles of charge ±e). This count is now exact, no longer a measured quantity.
A smartphone battery is rated 4,500 mAh — how much charge in coulombs?
4,500 mAh × 3.6 C/mAh = 16,200 C. That is the total charge delivered between full and empty. To know the energy you need the voltage too: at 3.85 V nominal it equals 17.33 Wh.
Why are battery capacities given in mAh instead of coulombs?
Because the practical question is run-time at a known load. "4,500 mAh" means the battery can supply 4.5 A for 1 hour, or 450 mA for 10 hours — directly readable as time. Coulombs (16,200 C) carry the same information but in less intuitive units for everyday use. Engineers do convert when they need to apply Faraday's laws or compute coulombic efficiency.
Are there positive and negative coulombs?
Yes. Charge is signed: a proton has +1 e ≈ +1.602 × 10⁻¹⁹ C, an electron has −1 e. When we say "1 C of charge" without sign in everyday speech, we usually mean the magnitude. In equations like Coulomb's law you must keep the sign.
Faraday and farad — same word, same unit?
No, they are entirely different. The faraday (symbol F or sometimes Fd) is a unit of charge: F ≈ 96,485 C, the charge of one mole of electrons. The farad (symbol F) is the SI unit of capacitance: 1 F = 1 C/V. The clash is unfortunate; context (charge vs capacitance) usually makes the intent clear.
Why does the elementary charge have an exact value now?
In the 2019 SI redefinition, the kilogram, ampere, kelvin, and mole were re-anchored to fixed values of seven defining constants. The elementary charge was fixed at e = 1.602 176 634 × 10⁻¹⁹ C with zero uncertainty. The ampere is now defined through this fixed e and the fixed second; the coulomb is one ampere-second.
How precise are the conversion factors here?
All factors are sourced from NIST SP 811 and the CODATA 2018/2019 recommended values. e and the SI prefix factors are exact by definition; 1 Ah = 3,600 C is exact (integer); 1 statC ≈ 3.335 640 95 × 10⁻¹⁰ C is exact via the speed-of-light definition. Display is rounded to ten significant figures.
Can I share a link to a specific conversion?
Yes. The URL updates as you change units and values, so you can copy the address bar after any conversion. Example: ?from=mAh&to=C&x=4500.
References
- NIST Special Publication 811 — Guide for the Use of the International System of Units (SI)
- BIPM SI Brochure (9th edition, 2019) — Defining constants and the redefined SI
- CODATA 2018 — Recommended value of the elementary charge e = 1.602176634 × 10⁻¹⁹ C (exact)
- ISO 80000-6:2008 — Quantities and units, Part 6: Electromagnetism
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