Coulomb Law Calculator
Calculate signed electrostatic force, force magnitude and attraction or repulsion between two point charges.
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Calculate force between two point charges
Enter two signed charges in microcoulombs, their center-to-center separation and the medium relative permittivity. The calculator converts the charges to coulombs and reports signed electrostatic force, absolute force magnitude and whether the signs imply attraction or repulsion. Keeping the sign and magnitude together helps users audit classroom problems and compare different charge combinations without losing the physical direction encoded by the inputs.
Keep the point-charge model within its limits
The inverse-square relationship assumes isolated point charges in a homogeneous linear medium. Extended conductors, nearby grounded surfaces, dielectric boundaries and charge redistribution can produce a different field. Use measured geometry or a suitable field solver when dimensions are not small compared with separation, and never treat this estimate as a high-voltage clearance or safety rating.
Frequently asked questions
What does a negative force mean?
Opposite charge signs produce attraction under the calculator sign convention.
Why is separation measured center to center?
The point-charge model places each charge at one geometric location.
What is relative permittivity?
It scales the vacuum interaction for an ideal homogeneous linear medium.