Coulomb's Law Calculator

Coulomb's law describes the electrostatic interaction between two ideal point charges. Force magnitude is proportional to the product of the charge magnitudes and inversely proportional to the square of their separation. In vacuum, the proportionality constant is approximately 8.98755 times 10 to the ninth newton square metres per square coulomb. This calculator converts the selected charge and distance units to coulombs and metres before applying the equation. Charge signs determine direction. Charges with the same sign repel, while opposite signs attract. The calculator reports force as a positive magnitude and labels the interaction separately. This avoids confusing a negative algebraic result with negative force magnitude. In a full vector calculation, the force acts along the line joining the charges, with direction assigned by a coordinate system. Distance has a powerful inverse-square influence. Doubling separation reduces force to one quarter; halving separation increases it fourfold. Charge enters linearly, so doubling one charge doubles force. These patterns help explain strong microscopic interactions and the rapid weakening of electrostatic effects with distance. Inputs must represent centre-to-centre separation between point-like charges. A material medium reduces the ideal vacuum interaction according to its relative dielectric constant. Air is often approximated as one, while water at common conditions is near eighty. The calculator divides force, field, and potential energy by the entered relative dielectric value. Real permittivity varies with temperature, frequency, composition, and field conditions, so use a value appropriate to the application. Electric field strength here is the magnitude of the field produced by charge 1 at charge 2's location. It equals the Coulomb constant times the absolute first charge divided by relative dielectric constant and distance squared. Potential energy equals the constant times the signed charge product divided by dielectric constant and distance. Unlike force magnitude, potential energy is negative for opposite charges and positive for like charges under the conventional zero-at-infinity reference. The point-charge model neglects finite object size, charge distribution, polarization geometry, nearby conductors, screening, and quantum effects. For several charges, calculate each vector contribution and use superposition rather than inserting total scalar charge blindly. The tool is suitable for physics exercises and preliminary estimates. High-voltage design, nanoscale modeling, and safety-critical electrostatics require geometry-aware numerical analysis and verified material properties.