Coulomb's Law Calculator
Calculate the electrostatic force between two point charges and see whether they attract or repel.
C
C
m
Attractive
- 1
Charge product |q1 × q2|
|0.000001 × -0.000002| = 0.000000000002 - 2
Separation squared r²
0.05² = 0.0025 - 3
Electrostatic force F = k · |q1·q2| / r²
8,987,500,000 × 0.000000000002 ÷ 0.0025 = 7.1900k = 8.9875 × 10⁹ N·m²/C² (Coulomb constant in vacuum)
How does this calculator work?
Coulomb's law gives the electrostatic force between two point charges as F = k·|q1·q2|/r², with k = 8.9875 × 10⁹ N·m²/C². Enter both charges in coulombs and their separation in meters; the calculator returns the force magnitude in newtons and whether the charges attract (opposite signs) or repel (like signs).
Formula
How this is calculated
Enter the two charges q1 and q2 in coulombs (C) and the separation distance r in meters (m). Charges may be positive or negative; you can type very small values in scientific notation such as 1e-6 for one microcoulomb.
The force magnitude is computed with Coulomb's law, F = k·|q1·q2|/r², where k = 8.9875 × 10⁹ N·m²/C² is the Coulomb constant in a vacuum. The absolute value of the product is used so the reported force is always a positive magnitude in newtons (N). The sign of the product q1·q2 determines the nature of the interaction: a positive product (like charges) gives a repulsive force, while a negative product (opposite charges) gives an attractive force.
The law assumes idealized point charges (or uniformly charged spheres) in vacuum, and force falls off with the inverse square of distance, so halving r quadruples the force. The separation must be greater than zero; r = 0 is undefined and the calculator requires a positive distance. If either charge is zero there is no force.
Frequently asked questions
Look at the sign of the product q1·q2. Like charges (both positive or both negative) repel; opposite charges attract. The magnitude is the same either way.
It uses the vacuum Coulomb constant k = 8.9875 × 10⁹ N·m²/C². In a medium with relative permittivity εr, divide the result by εr.
Coulomb's law is an inverse-square law: force is proportional to 1/r². Halving the distance multiplies the force by four.
Also known as
TG we-Calculate Editorial Team. (2026). Coulomb's Law Calculator [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/coulomb-law-calculator
TG we-Calculate Editorial Team. "Coulomb's Law Calculator." TG we-Calculate. 2026. https://we-calculate.com/calculator/coulomb-law-calculator.
TG we-Calculate Editorial Team, "Coulomb's Law Calculator," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/coulomb-law-calculator
@misc{wecalculate_coulomb_law_calculator, title = {Coulomb's Law Calculator}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/coulomb-law-calculator}}, year = {2026}, note = {TG we-Calculate} }
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