Coulomb's law gives the force between two point charges: it is proportional to the product of the charges and inversely proportional to the square of the distance between them. This calculator takes the charges in microcoulombs (µC) and the distance in metres.
A positive result means the charges have the same sign and repel; a negative result means they have opposite signs and attract. The calculation assumes the charges are in air or a vacuum.
| Charge 1 (q₁) | 2 µC |
| Charge 2 (q₂) | -3 µC |
| Distance between charges (r) | 0.1 m |
| Size of force (N) | 5.39253 |
| Force with sign (N): + repel, − attract | -5.39253 |
They attract with a force of 5.39253 N.
Try this example →| Charge 1 (q₁) | 1 µC |
| Charge 2 (q₂) | 1 µC |
| Distance between charges (r) | 1 m |
| Size of force (N) | 0.00898755 |
| Force with sign (N): + repel, − attract | 0.00898755 |
They repel with 0.00898755 N.
Try this example →The force between two point charges is F = kq₁q₂/r²: proportional to the product of the charges and inversely proportional to the square of their separation.
k = 1/(4πε₀) ≈ 8.988 × 10⁹ N·m²/C², often rounded to 9 × 10⁹.
The coulomb (C). The charge of an electron is −1.602 × 10⁻¹⁹ C.
It becomes four times larger.