Coulomb's Law Calculator

This calculator finds the electrostatic force between two electric charges using Coulomb's law, the electrical counterpart to Newton's law of gravity. Just as masses attract through gravity, electric charges exert forces on each other, and Coulomb's law describes them precisely: the force is proportional to the product of the two charges and inversely proportional to the square of the distance between them. Unlike gravity, which only ever attracts, electric forces can both attract and repel: opposite charges, one positive and one negative, pull together, while like charges, both positive or both negative, push apart. The force is also vastly stronger than gravity, governed by Coulomb's constant, a large number, which is why electrical forces dominate the behaviour of atoms, molecules and materials. This tool computes it for you. You enter the two charges in coulombs, using scientific notation for the typically tiny values involved, such as microcoulombs, and the distance between them in metres, and the calculator returns the magnitude of the force, states whether it is attractive or repulsive based on the signs of the charges, and shows the electric field produced by the first charge at that distance. The results update as you type. Use it for physics homework, for understanding electrostatics, or for any problem involving charged particles. The inverse-square form means the force falls away quickly with distance: moving the charges twice as far apart cuts the force to a quarter. Because real charges are usually small fractions of a coulomb, expect to work in microcoulombs or smaller, which the scientific notation input makes easy. A positive product of charges indicates repulsion, a negative product attraction.

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F = k x q1 x q2 / r squared, with k = 8.988 x 10^9. Like charges repel, opposite charges attract. Use scientific notation for small charges (e.g. 1e-6).