Coulomb's Law Calculator
Electrostatic force, and how far it beats gravity.
Work out Coulomb's Law. Electrostatic force, and how far it beats gravity. Shows the working, not just the answer.
Scientific notation works. 1 µC is 1e-6. Use a negative value for a negative charge.
Electrostatic force — repulsive
0.8988 N
Like charges push apart
Same inverse-square form as gravity, and about 10³⁶ times stronger between two protons. That ratio is why gravity is completely irrelevant inside an atom and completely dominant between planets — charges come in both signs and cancel, mass does not. It is also why solids are rigid. What stops your hand passing through a table is electrostatic repulsion between electron clouds, not any physical contact. Unlike gravity, the force can be either sign, so potential energy is positive for like charges and negative for opposite ones.
How the Coulomb's Law Calculator works
Enter two charges and their separation for the electrostatic force between them, whether it attracts or repels, and the ratio to gravity at the same distance. That ratio is about 10³⁶, which is the number that explains why atoms work the way they do.
Also known as: electrostatic force calculator · force between two charges · f = kq1q2/r2 · electric force calculator
Frequently asked questions
What is Coulomb's law?
F = kq₁q₂/r², with k at 8.99 × 10⁹ N·m²/C². Same inverse-square form as gravity, but the force can be either attractive or repulsive.
How much stronger is electrostatic force than gravity?
Between two protons, about 10³⁶ times. That is why gravity is completely irrelevant inside an atom and completely dominant between planets, where charges cancel and mass does not.
Why can't I push my hand through a table?
Electrostatic repulsion between electron clouds. There is no physical contact in the everyday sense — what feels solid is the electromagnetic force resisting compression.
How big is one coulomb?
Enormous. Two 1 C charges a metre apart would repel with about 9 billion newtons. Real static charges are microcoulombs, which is why the numbers in problems look so small.
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