The electric field calculator computes the electric field strength at a distance from a point charge using E = kq/r², where k = 8.99 × 10⁹ N·m²/C². Enter charge in Coulombs or microcoulombs and distance in meters or cm.
Electric Field Calculator (E = kq/r²)
How to Use the Electric Field Calculator
This calculator finds the electric field strength at a point in space due to a single point charge. The electric field E is measured in N/C (equivalently V/m).
Example Calculation
A 5 μC charge at 10 cm distance: E = (8.99×10⁹ × 5×10⁻⁶) / (0.1)² = 44,950 / 0.01 = 4,495,000 N/C = 4.495 MN/C. The force on a 1 μC test charge at this point would be F = qE = 10⁻⁶ × 4.495×10⁶ = 4.495 N.
Direction of Electric Field
The field points radially away from positive charges and toward negative charges. For opposite charges, use negative q values — the calculator will show the direction by the sign of q.
Superposition
For multiple charges, calculate each field separately and add them as vectors (components). This tool handles individual point charges; add results manually for multiple source charges.
Frequently Asked Questions
What is the electric field formula?
Electric field E = kq/r², where k = 8.99 × 10⁹ N·m²/C² (Coulomb's constant), q is the source charge in Coulombs, and r is the distance in meters. E is measured in N/C (newtons per coulomb) or equivalently V/m (volts per meter). The field points away from positive charges and toward negative charges.
What is the difference between electric field and electric force?
Electric field E is a property of space — it describes the force per unit charge at a point. Electric force F = qE is the actual force on a charge q placed in the field. A 1 μC charge at a point where E = 1000 N/C experiences force F = 0.001 N.
Is this calculator free?
Yes, completely free with no signup required. All calculations run in your browser.
Is my data private?
Yes. All calculations run locally. Nothing is transmitted.
What units are used for charge in this calculator?
Charge is entered in Coulombs (C) or microcoulombs (μC). One microcoulomb = 10⁻⁶ C. A proton has charge +1.602 × 10⁻¹⁹ C. Typical static electricity charges are on the order of nanocoulombs (10⁻⁹ C) to microcoulombs (10⁻⁶ C).