Electric Field Calculator

The Field That Exists Before Anything Else Is There

An electric field describes the force a charge would experience at a given point in space, whether or not a second charge is actually sitting there to feel it. That's what makes it a field rather than just a force: it's a property of the space around a charge. This calculator computes field strength two ways — from a measured force on a known charge, or directly from a point charge's magnitude and distance using Coulomb's law.

The Formulas

From force and charge: E = F / q
From a point charge: E = k × Q / r²

where E is electric field strength in newtons per coulomb (N/C), F is force in newtons, q and Q are charge in coulombs, r is distance from the charge in meters, and k is Coulomb's constant, 8.99 × 10⁹ N·m²/C².

A Worked Example

Field strength from a 2 µC point charge at increasing distance
Distance	Field Strength (E = kQ/r²)
0.5 m	7.19 × 10⁴ N/C

E = (8.99 × 10⁹ × 2 × 10^-6) / 0.5² = 71,920 N/C. Field strength falls off with the square of distance — doubling the distance cuts it to a quarter.

Reference Field Strengths

Approximate electric field strengths in nature and engineering
Source / Condition	Typical Field Strength
Earth's fair-weather field at the surface	~100 V/m
Beneath a thunderstorm	~10,000–15,000 V/m
Dielectric breakdown of dry air	~3 × 10⁶ V/m

V/m and N/C are equivalent units for electric field strength.

Where This Calculation Matters

Electrostatic discharge (ESD) protection — understanding field strengths near charged components helps in designing shielding and grounding.
Capacitor design — the field between capacitor plates determines the maximum voltage before the dielectric breaks down.
High-voltage equipment clearances — engineers use field calculations to set safe distances around charged conductors and equipment.
Physics coursework — verifying textbook and lab problems involving point charges and Coulomb's law.

How to Use This Calculator

Choose the calculation mode: From Force and Charge, or From Point Charge.
For Force and Charge, enter the Force in newtons and the Charge in coulombs.
For Point Charge, enter the Point Charge Q in coulombs and the Distance r in meters.
Select Calculate to see the resulting field strength.

Related Calculations

Electric and magnetic fields often appear together in electromagnetism problems — see the Magnetic Field Calculator for the current-generated counterpart.