Calculates the electrostatic force between two point charges — the electrical counterpart to gravitational force between two masses.
How it works
Coulomb’s constant is multiplied by both charges and divided by the square of the distance between them.
What this does not include
This treats both charges as point charges — real extended objects with distributed charge require more advanced methods for precise force calculations.
How to use this calculator
- Enter both charges and the distance between them.
A worked example
Charges of 1×10⁻⁶ C and 2×10⁻⁶ C, 0.1 m apart: force = 1.798 N.
Charges of 3×10⁻⁶ C each, only 0.05 m apart: force = 32.364 N — much larger, since halving the distance roughly quadruples the force.
What the variables mean
| Variable | Meaning |
|---|---|
| q1, q2 | The two point charges, in coulombs |
| Distance | Separation between the charges, in meters |
Edge cases worth knowing
Force falls off with the square of distance, not linearly. The second example shows this directly: halving the distance from 0.1 m to 0.05 m doesn’t double the force, it roughly quadruples it.
Zero distance makes the force infinite, which has no physical meaning — the calculator declines to show a result rather than an undefined value.
Frequently asked questions
Why does the force decrease so quickly with distance?
Because distance is squared in the denominator — doubling the distance reduces the force to one quarter of its original strength, the same inverse-square pattern gravity follows.
What does a negative force result mean?
If one charge is positive and the other negative, the calculated force is attractive rather than repulsive — the formula’s sign convention reflects that.
How is this similar to gravitational force?
Both follow the same inverse-square-law shape, just with a different constant and different property of the objects (charge instead of mass) driving the force.
