Coulomb's Law Calculator
Compute electrostatic force between two point charges: F = k |q1 q2| / r². Default 1 µC and 1 µC at 0.1 m separation. Uses k = 8.9875517923×10⁹ N·m²/C². Informational physics only.
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How to use Coulomb's law calculator
- Enter both charges and pick C, µC, or nC.
- Enter center-to-center distance in meters.
- Read force in newtons. The page uses absolute charge product.
- Point charges in vacuum or air approximation only. Nothing is uploaded.
Coulomb's law
F = k |q1 q2| / r²
| Force | Newtons along the line joining charges |
|---|---|
| Constant k | 8.9875517923×10⁹ N·m²/C² in SI |
| Distance | Meters between point centers |
| Charges | Signed values OK; force uses magnitude product |
| Default | 1 µC pair at 0.1 m |
| Approval | Informational. Not a lab safety review. |
Inverse square law
Force magnitude scales with the product of charges and falls with the square of distance. Doubling distance cuts force by four.
Charge units
Enter µC for bench-scale static demos or C for SI textbook values. The engine converts to coulombs before applying k.
Attractive vs repulsive
Like signs repel; opposite signs attract. This page reports magnitude in newtons. Direction follows the sign rule in your diagram.
Different from Q = C V
Capacitor charge from voltage is capacitance to charge. Coulomb's law is force between free charges in space.
Limits
Point charges, no medium correction beyond free-space k.
The formula runs in this tab. CZNull does not receive the numbers.
Informational only. Not wiring, code, or manufacturer approval. See the disclaimer.