Coulomb's Law Calculator
Electrostatic force between two point charges, the field of the first, and their potential energy.
Results
Force
-13.48133
N
Force
13.48133
N
Electric field
4,493,775.89
V/m
Energy
-1.348133
J
What this tool does
A negative result means attraction and a positive one repulsion, because opposite charges give a negative product. The law has exactly the same inverse-square shape as gravity, but electrostatic force is some thirty-six orders of magnitude stronger — which is why a small comb lifts paper against the pull of the entire Earth.
Formula
F = k × q₁ × q₂ ÷ r² (k ≈ 8,987 551 79 × 10⁹ N·m²/C²)
Variables
| Symbol | Meaning | Unit |
|---|---|---|
q1 | First charge | µC |
q2 | Second charge | µC |
r | Distance | cm |
F | Force | N |
FA | Force | N |
EF | Electric field | V/m |
PE | Energy | J |
Worked example
- First charge5 µC
- Second charge-3 µC
- Distance10 cm
- Force-13.48133 N
- Force13.48133 N
- Electric field4,493,775.89 V/m
- Energy-1.348133 J
Limitations
- The formula assumes ideal conditions: no friction losses, no air resistance and no efficiency losses unless you enter them.
- Mixing units is the most common source of error. Convert every input to the units shown next to each field before calculating.