What is Coulomb's constant?

Coulomb's constant k ≈ 8.9875 × 10⁹ N·m²/C² (sometimes written as 1/(4πε₀)). It relates charge and distance to the resulting electric force or field strength in SI units.

What units does the result use?

The electric field strength is given in newtons per coulomb (N/C), which is identical to volts per meter (V/m). Both units describe the force per unit positive test charge.

What direction does the field point?

By convention, the field points away from a positive charge and toward a negative charge. This calculator notes the direction based on the sign of the charge you enter.

Why does distance have such a large effect?

The formula is E = kQ/r², so the field falls off with the square of the distance. Doubling the distance reduces the field to one quarter of its original value — the classic inverse-square law.

Can I enter the charge in microcoulombs?

Yes. Select μC from the charge unit drop-down and the calculator converts to coulombs automatically before applying the formula.

Electric Field Point Charge Calculator

Name: Electric Field Point Charge Calculator
Availability: InStock
Author: Nham Vu

Enter a point charge and distance to instantly compute the electric field strength (E = kQ/r²) in N/C or V/m.

Input Values

Point Charge (Q)

Enter negative value for a negative charge.

Distance (r)

Result

Enter values and click Calculate.

Copied!

Summary

Enter a point charge and distance to instantly compute the electric field strength (E = kQ/r²) in N/C or V/m.

How it works

Enter the point charge value (Q) in coulombs, microcoulombs, or nanocoulombs.
Enter the distance (r) from the charge to the point of interest in meters or centimeters.
The calculator applies Coulomb's constant k = 8.9875 × 10⁹ N·m²/C².
Results display field strength in N/C (equivalent to V/m) with a full formula breakdown.
Field direction is shown as away from the charge (positive Q) or toward it (negative Q).

Use cases

Verify electric field homework problems and exam solutions.
Explore how field strength falls off with the inverse-square law.
Compare fields from different charge magnitudes at the same distance.
Understand field direction conventions for positive and negative charges.
Quickly convert between microcoulomb/nanocoulomb inputs and SI results.
Visualize relative field strength in electrostatics lab prep.

Frequently Asked Questions

Last updated: 2026-06-10 · Reviewed by Nham Vu