Coulomb's Law Calculator
Calculate electrostatic force, electric field, and potential energy between point charges in vacuum or dielectric media ($F = \frac{k}{\varepsilon_r} \frac{q_1 q_2}{r^2}$), solve for missing variables, or compute 3-charge superposition.
Enter charge magnitudes and separation distance. Select a unit prefix or dielectric medium to model real-world electrostatic systems.
Enter both charges and a distance to see the force, field, and energy.
Select which variable to solve for ($q_1$, $q_2$, $r$, or $\varepsilon_r$), then enter the remaining known quantities.
Pick which variable to solve for, then fill in the rest.
Uses current charge magnitudes and medium permittivity. Shows how force decreases with $1/r^2$ as separation increases.
Adjust charges on the Force tab to reshape this curve.
Calculate the net electrostatic force acting on Charge 3 ($q_3$) positioned along a straight line between or near $q_1$ and $q_2$.
By the superposition principle, vector components add linearly.
Electromagnetism & Fundamental Physical Constants
This calculator implements Coulomb's electrostatic force equation ($F = \frac{1}{4\pi\varepsilon_0 \varepsilon_r} \frac{q_1 q_2}{r^2}$) using exact 2018 CODATA fundamental constants maintained by the National Institute of Standards and Technology (NIST).
Academic References & Peer-Reviewed Sources
- Coulomb, C. A. (1785). Premier Mémoire sur l'Électricité et le Magnétisme. Histoire de l'Académie Royale des Sciences, pp. 569–577.
- NIST / CODATA (2018). Fundamental Physical Constants: Coulomb Constant & Vacuum Permittivity. National Institute of Standards and Technology.
- Halliday, D., Resnick, R., & Walker, J. (2021). Fundamentals of Physics (12th ed.). Wiley. Chapter 21: Electric Charge and Coulomb's Law.
- Griffiths, D. J. (2017). Introduction to Electrodynamics (4th ed.). Cambridge University Press. Chapter 2: Electrostatics.