Calculate the electrostatic force, potential energy and field between two point charges from their charges and separation.
Enter charges in microcoulombs (µC) and separation in centimetres. Like charges repel, opposite charges attract; the force follows an inverse-square law, so halving the distance quadruples the force.
Electrostatic force
How to use this tool
Type each charge in microcoulombs; use a minus sign for a negative charge.
Type the distance between the charge centres in centimetres.
The result gives the force magnitude and whether the charges attract or repel.
Potential energy and the electric field at the second charge are shown for homework and circuit analysis.
Formula & worked example
Two 1 µC charges 10 cm apart repel with about 0.899 N, and their electrostatic potential energy is about 0.0899 J.
Limitations — read this before you rely on it
This treats the charges as points in a vacuum. Real materials reduce the force by their relative permittivity, and extended charge distributions need integration, not this point formula.
Frequently asked questions
The force between two point charges is proportional to the product of the charges and inversely proportional to the square of their separation.
Like charges repel and opposite charges attract; the force acts along the line joining the charges.
The force falls to one quarter, because of the inverse-square dependence on distance.
k ≈ 8.988 × 10⁹ N·m²/C² in vacuum, equal to 1 / (4πε₀).
Yes — in a dielectric the force is reduced by the relative permittivity; this calculator assumes vacuum (air is close enough for most purposes).