Four calculators, one panel.
Pick a mode below — everything recalculates live as you type, and every result explains itself.
How much current flows — 2 A is a fast phone charger, 0.5 A a slow one.
How long it flows — pick the unit that fits the job.
The charge moved — enter this when solving for current or time.
Any count works — 1 for a single electron, or 6.24e18 for a full coulomb.
Electrons make the charge negative, protons positive.
Negative charge → electrons; positive → protons (or missing electrons).
Signs matter — like charges repel, opposite charges attract. Use e for single particles.
Mix units freely — the maths doesn't care.
The gap between the two charges — picometres for atoms, metres for labs.
Any size works — negative values convert too.
Every other unit still appears in the results table.
From question to answer in four moves.
No setup, no sign-up — open a tab, type, done.
Pick a mode
Four tabs cover the four everyday charge questions: Q = It, counting particles, the force between charges, and plain unit conversion.
Enter your values
Type your numbers and choose units from the dropdowns — milliamps or microamps, milliseconds to hours, picocoulombs to faradays.
Read the answer
Results update live as you type, in sensible units — with electron counts, force direction and battery-style mAh included where they matter.
Check the working
Every answer shows the formula with your numbers plugged in — and impossible inputs get a clear warning instead of a wrong number.
Three formulas do all the work.
Everything this calculator does rests on three short equations — here they are, in plain sight.
Charge from current
One ampere flowing for one second moves one coulomb — the definition of the unit. Rearranged, it also finds current (I = Q ÷ t) or time (t = Q ÷ I).
Charge is quantized
Charge only comes in whole multiples of the elementary charge e — the size of one proton (+) or one electron (−). One coulomb is about 6.24 × 1018 of them.
Coulomb's law
The force between two point charges, with k ≈ 8.988 × 109 N·m²/C². Like charges repel, opposites attract, and halving the distance quadruples the force.
Questions, answered.
The essentials of electric charge — what a coulomb is, where electrons fit in, and how the maths connects. Tap any question to expand it.
What is electric charge, and what is a coulomb?+
Electric charge is the fundamental property that makes particles push or pull on each other through the electromagnetic force. Its SI unit is the coulomb (C): one coulomb is the charge moved by a current of one ampere flowing for one second, so 1 C = 1 A·s. A single electron carries −1.602176634 × 10−19 C — the elementary charge.
How do I calculate charge from current and time?+
Use Q = I × t: multiply the current in amperes by the time in seconds. A 2 A current flowing for 10 s moves 20 C of charge. Convert units first — 30 minutes is 1800 s, and 500 mA is 0.5 A. The calculator handles A, mA, µA and ms/s/min/h automatically and can rearrange the formula to find I or t instead.
How many electrons are in one coulomb?+
About 6.24 × 1018 — six billion billion. Divide one coulomb by the elementary charge: 1 ÷ (1.602176634 × 10−19) ≈ 6.242 × 1018. That is why everyday charges involve enormous particle counts even though the coulomb itself is a modest, everyday-sized unit.
How do I find the number of electrons in a charge?+
Divide the charge by the elementary charge: n = Q ÷ e. A −3.2 µC charge, for instance, means 3.2 × 10−6 ÷ 1.602 × 10−19 ≈ 2.0 × 1013 electrons; the minus sign tells you electrons are in surplus. The Electrons mode does this instantly and works in both directions.
How does Coulomb's law calculate the force between charges?+
Coulomb's law is F = k · q₁ · q₂ ÷ r², where k ≈ 8.988 × 109 N·m²/C². Two 1 µC charges held 1 cm apart push on each other with about 90 N. Like charges repel, opposite charges attract, and halving the distance quadruples the force.
How do I convert mAh to coulombs?+
1 Ah = 3600 C, so 1 mAh = 3.6 C. Multiply the mAh value by 3.6: a 3000 mAh phone battery stores 10,800 C. The Unit converter mode also handles µC, nC, pC, elementary charges, faradays and moles of electrons in a single step.
Can electric charge be negative or a fraction of the elementary charge?+
Charge comes in two signs — negative (a surplus of electrons) and positive (a deficit of electrons, or a surplus of protons) — but its size is quantized: every charge ever measured is a whole-number multiple of e. You will never find half an electron's charge on its own. Macroscopic charges can still take almost any value because the particle counts involved are so huge.
Is this calculator free, and is my data sent anywhere?+
It is completely free and runs entirely in your browser — nothing you type is uploaded, logged, or sent to a server. No account, no sign-up, no limits.