PhysicsCalcs
Electricity

Electric Field Calculator

Calculate the electric field strength from force and charge, or from a point source charge at a given distance. Enter known values, choose units, and see the formula with direction notes.

Interactive calculator

Electric Field Calculator

Calculate electric field strength, force, charge, or distance. Enter known values and click Calculate.

Force on the test charge

Positive test charge magnitude

Your result will appear here.

Choose a calculation mode, fill in the known values, and click Calculate.

Quick Guide

  • Choose what to calculate.
  • Negative charges are allowed for source charges.
  • Relative permittivity is optional (defaults to 1).
  • Click Calculate.

Table of Contents

Key Takeaways

  • An electric field describes the force per unit positive charge at a point in space.
  • E = F / q gives the field from force and charge.
  • E = k|Q| / r² gives the field from a point source charge.
  • The field points away from positive charges and toward negative charges.
  • Electric field units are N/C or equivalently V/m.
  • The calculator supports optional relative permittivity for different media.

What Is an Electric Field?

An electric field is a vector field surrounding an electric charge that describes the force a positive test charge would experience at each point in space. It is a fundamental concept in electrostatics and electromagnetism.

The strength of the electric field at a point tells you how strong the electrostatic force would be on a unit positive charge placed there. Stronger fields mean stronger forces.

Electric Field Formulas

E=FqE=\frac{F}{q}

Field from force and test charge. The defining relationship.

E=k∣Q∣r2E=k\frac{|Q|}{r^2}

Field from a point source charge at distance r.

F=qEF=qE

Force on a charge in an electric field.

r=k∣Q∣Er=\sqrt{\frac{k|Q|}{E}}

Distance at which a given field strength occurs.

Electric Field Infographic explaining point charge fields

How to Use the Electric Field Calculator

  1. 1Select what to calculate from the dropdown.
  2. 2Enter the known values.
  3. 3Choose units.
  4. 4Click Calculate.
  5. 5Review the result and direction note.

Example Calculations

Field from force and charge

F = 0.5 N on a 2 μC test charge. E = 0.5 / 2×10−&sup6; = 250,000 N/C = 250 kV/m.

Field from point charge

Q = +1 μC at r = 0.5 m. E = 8.99×10&sup9; × 10−&sup6; / 0.25 = 35,960 N/C. Field points away from Q.

Electric Field Direction

The electric field points away from positive source charges and toward negative source charges. A positive test charge placed in the field accelerates in the field direction; a negative test charge accelerates opposite to it.

The calculator shows the direction note alongside the magnitude.

Electric Field vs Electric Force

The electric field is a property of space created by a source charge. The force is what happens when a second charge is placed in that field. The relationship is F = qE. The field exists regardless of whether a test charge is present.

Where This Calculator Is Useful

Electric field calculations are used in physics education, electrostatics problems, capacitor design, understanding charge distributions, electronics, and fields-based engineering analysis.

Accuracy and Limitations

This calculator uses classical electrostatics formulas for point charges.

Limitations: applies to point charges only, no dynamic or magnetic effects, no quantum corrections at atomic scales, and no vector addition for multiple charges.

Frequently Asked Questions

What is an electric field?›

An electric field is a region around a charged object where other charges experience a force. It is defined as the force per unit positive test charge: E = F/q.

What are the units of electric field?›

N/C (newtons per coulomb) or equivalently V/m (volts per metre). Both describe the same quantity.

What is the formula for electric field?›

For force-based: E = F/q. For a point charge source: E = k|Q|/r².

Which direction does the electric field point?›

Away from positive charges, toward negative charges. A positive test charge accelerates in the direction of the field.

How is electric field related to Coulomb’s Law?›

Coulomb’s Law gives the force between two charges. The electric field E = k|Q|/r² is the force per unit charge that Q creates, regardless of the test charge.

What is the difference between electric field and electric force?›

The electric field exists at every point in space around a charge. The force is what a specific charge experiences when placed in that field: F = qE.

Does permittivity affect the field?›

Yes. In a dielectric medium with relative permittivity εᵣ, the field is reduced by a factor of εᵣ.

Can the electric field be zero between two charges?›

Yes. For two like charges, there is a point between them where the fields cancel. For opposite charges, the cancellation point is outside the pair.

Does this calculator handle multiple charges?›

Not directly. For multiple source charges, calculate each field separately and add them as vectors.

Is this calculator useful for capacitors?›

For a parallel-plate capacitor, the uniform field is E = V/d. This calculator focuses on point charges and force-based definitions.

Sources / References

  1. OpenStax College Physics 2e: Electric Field
  2. HyperPhysics: Electric Field
  3. Khan Academy: Electric Field
Manish Kumar

Author & technical reviewer

Manish Kumar

PhysicsCalcs tools are reviewed with an educational focus: clear formulas, transparent assumptions, and practical context for students and science learners.

Learn more about Manish