⚡Coulomb's Law Calculator
Find the electrostatic force between two point charges, or solve for charge or distance.
Runs entirely in your browser. No data is sent to a server.
Free Coulomb's Law Calculator
Working through an electrostatics problem? Our free Coulomb's law calculator finds the force between two point charges instantly. Enter both charges and the distance between them, and it calculates the electrostatic force — telling you clearly whether it's attractive or repulsive based on the charge signs, not just a number.
Charges are often tiny, so the calculator supports microcoulombs, nanocoulombs, and scientific notation without losing precision. Every result comes with the formula shown, including Coulomb's constant, and the full substitution with your actual values, so you can follow the working or check your own answer.
Whether you're studying electrostatics for a physics class or verifying a circuit-adjacent calculation, this tool gives accurate results with clear reasoning. No sign-up, no downloads, no limits — just fast, correct answers. See the About page or the FAQ for more.
About the Coulomb's Law Calculator
Features
Solve for any variable
Force, either charge, or distance.
Attractive/repulsive
Classified from the signs of both charges.
Unit support
Charge in C, mC, µC, nC; distance in m, cm, mm.
Step-by-step working
Formula shown with full substitution.
Frequently Asked Questions
How does the Coulomb's law calculator work?
Enter two charges and the distance between them, and it applies F = kq1q2/r² to compute the electrostatic force.
Is it free?
Completely free, no sign-up, downloads, or limits.
What is Coulomb's constant?
k ≈ 8.988×10⁹ N·m²/C², a fixed constant in Coulomb's law relating charge, distance, and force.
How do I know if the force is attractive or repulsive?
The calculator checks the signs of both charges: opposite signs mean attraction, same signs mean repulsion, and it states this explicitly.
Does it handle tiny charge values?
Yes, charges can be entered in microcoulombs, nanocoulombs, or scientific notation.
Does it show the steps?
Yes, the formula — including the value of k — and substitution with your actual values are shown.
What if I enter zero distance?
This is flagged as invalid since it produces an undefined (infinite) force.
Can it solve for charge or distance instead of force?
Yes, choose which quantity to solve for and enter the other three.
Is my data stored?
No; everything runs in your browser and isn't stored or sent anywhere.
Does it work on mobile?
Yes, fully responsive on all screen sizes.