Coulomb Force Calculator
Calculate electrostatic force magnitude, attraction or repulsion, and potential energy for two point charges in a uniform dielectric.
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Result
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Calculation steps
Work through one step at a time or reveal the complete calculation. The steps use your current inputs.
How to calculate
Convert both charges and separation to SI. Scale the vacuum Coulomb constant by the entered relative permittivity, preserve the charge-product sign for interaction and energy, and report force magnitude separately.
|F|=|q1q2|/(4πε0εr r^2); U=q1q2/(4πε0εr r)
Worked example
Charges +1 μC and −1 μC separated by 10 cm in vacuum have an attractive force magnitude of about 0.8988 N and potential energy about −0.08988 J.
Assumptions and input details
Point charges at a nonzero fixed separation in a homogeneous, linear, isotropic dielectric with entered relative permittivity. The force shown is a magnitude; attraction or repulsion comes from the signs. Material breakdown, screening, boundaries, distributed charge and quantum effects are excluded.
References: OpenStax University Physics Volume 2: Coulomb’s law
Unit definitions
Unit selection is independent of language. Each selector contains only units for its physical quantity. Calculations use defined base units internally.
Choose from 23 length definitions, including explicitly labelled regional measures. Area conversions square the length factor; geometric volumes cube it.
Regional measures are not interchangeable merely because their names look similar. This is a documented selection, not a claim to include every historical unit.
NIST measurement tables · Japanese traditional units · Mainland China and Hong Kong unit distinctions
Using this calculator
Can I enter my own problem?
Yes. Replace the example values with your own inputs. The result, calculation steps, tables and applicable diagrams update from those inputs. Blank or invalid values clear the result; example values are never silently substituted for missing inputs.
Are the results exact?
Results use floating-point arithmetic and displayed rounding. Read the formula, assumptions and any stated data precision before interpreting the result.
Is my input uploaded?
The calculation runs in your browser. No account, file upload or external AI service is required. Inputs are not saved between page reloads.
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