Coulomb’s Law Calculator
⚡ Electricity & magnetism. Use the Coulomb’s law formula to find force, charge 1, charge 2, distance: pick the value you want, type the others, and the answer updates as you go.
k = 8.99 × 10⁹ N m²/C². Like charges repel (F > 0), unlike attract.
Pick the ○ next to the value you want to find, fill in the others, and it solves as you type.
What each letter means
| Quantity | Unit |
|---|---|
| Force | N |
| Charge 1 | C |
| Charge 2 | C |
| Distance | m |
Worked example
Find the force when Charge 1 = 1 × 10⁻⁶ C, Charge 2 = 1 × 10⁻⁶ C, Distance = 0.1 m.
Using F = (k q1 q2)/r²: Force = 0.89875 N.
Frequently asked questions
What is the formula for Coulomb’s law?
F = (k q1 q2)/r². k = 8.99 × 10⁹ N m²/C². Like charges repel (F > 0), unlike attract.
What do the letters stand for, and what units are used?
Force in N, Charge 1 in C, Charge 2 in C, Distance in m.
How do you calculate force?
Put the values into F = (k q1 q2)/r². For example, with Charge 1 = 1 × 10⁻⁶ C, Charge 2 = 1 × 10⁻⁶ C, Distance = 0.1 m, force = 0.89875 N.
Can I solve for a different value?
Yes. In the calculator above, pick the circle next to any value (force, charge 1, charge 2, distance) and fill in the others: it rearranges the formula for you.
