Coulomb's Law Calculator
Calculate the electrostatic force between two point charges using Coulomb's law and the distance separating them.
Last reviewed by the Radiatus Cloud team
Calculate the electrostatic force between two point charges.
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Calculate electrostatic force
Coulomb's law describes the force between two electric point charges. The force is proportional to the product of the charges and inversely proportional to the square of the distance between them, scaled by Coulomb's constant, about 8.99 times ten to the nine. This calculator computes the magnitude of the force and tells you whether it is attractive or repulsive: like charges repel, while opposite charges attract. The structure of the law closely mirrors Newton's law of gravitation.
Charges are measured in coulombs, a large unit, so practical charges are often microcoulombs or smaller.
Electric forces
Coulomb's law is the foundation of electrostatics, explaining the forces that hold atoms and molecules together, the behaviour of charged particles, and the operation of countless devices. Like gravity, it follows an inverse-square law with distance, but electric forces are vastly stronger and can be either attractive or repulsive, unlike gravity which only attracts.
The sign of the product of the charges determines the nature of the force, which the calculator reports. Results can span many orders of magnitude, so scientific notation is used. All calculation happens locally in your browser.
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Frequently Asked Questions
What is Coulomb\'s law?
It states that the force between two point charges is proportional to the product of the charges and inversely proportional to the square of the distance between them.
When is the force attractive or repulsive?
Opposite charges attract and like charges repel. The sign of the product of the two charges determines which, as the tool reports.
What is Coulomb\'s constant?
It is about 8.99 times ten to the nine newton metres squared per coulomb squared, setting the strength of the electrostatic force.
How does Coulomb\'s law compare to gravity?
Both follow an inverse-square law, but electric forces are far stronger and can attract or repel, whereas gravity only attracts.
What units should I use?
Charges in coulombs and distance in metres give the force in newtons. Small charges are often entered in scientific notation.
Privacy & Security
Everything runs in your browser; nothing is uploaded.
How to Use
Enter the two charges in coulombs and the distance in metres.
Disclaimer: This tool is provided "as is" without warranty of any kind. Results are for educational and utility purposes.