Electric Field Calculator
Find the electric field from a point charge.
Results update as you type.
How it works
The electric field describes the force a charge would exert on other charges around it, and this calculator finds the field strength from a point charge at a given distance. You enter the charge in coulombs and the distance from it in meters, and it returns the electric field strength in newtons per coulomb. The field equals Coulomb's constant, approximately 8.99 billion newton-meters squared per coulomb squared, times the magnitude of the charge, divided by the square of the distance. This inverse-square relationship means the field falls off rapidly with distance: moving twice as far away reduces the field to a quarter, and three times as far to a ninth. The electric field is a vector pointing radially outward from a positive charge and inward toward a negative one, and its strength tells you how strong a force a unit test charge placed there would feel. Electric fields are central to electromagnetism, underlying how charges interact, how capacitors and circuits work, and how forces propagate without contact. Because a coulomb is a very large amount of charge, real charges are often tiny fractions, so values may be in microcoulombs or nanocoulombs, which must be converted to coulombs. Enter the charge and distance to compute the electric field strength.
E = k·|Q| / r²
The electric field from a point charge equals Coulomb's constant, about 8.99 billion, times the magnitude of the charge, divided by the square of the distance from the charge. The field weakens with the square of the distance, so doubling the distance quarters the field. It points away from a positive charge and toward a negative one.
Source:Electromagnetism
We review all our tools from time to time to ensure accuracy.
Worked example
How to use this calculator
- 1
Enter your values
Enter charge and distance.
- 2
Adjust the options
Fine-tune any options to match your situation.
- 3
Read your result
Electric field strength updates instantly as you type — no button to press.
Frequently asked questions
What is an electric field?
An electric field is a region around a charge where other charges experience a force. Its strength at a point tells you the force a unit positive test charge would feel there, in newtons per coulomb. The field points away from positive charges and toward negative ones, describing how charges influence their surroundings.
How do you calculate the electric field of a point charge?
Multiply Coulomb's constant, about 8.99 billion, by the magnitude of the charge, then divide by the square of the distance from the charge. The calculator does this from your charge and distance inputs. Remember to convert microcoulombs or nanocoulombs to coulombs, since a full coulomb is a very large charge.
Why does the field follow an inverse-square law?
The field from a point charge spreads out over the surface of an expanding sphere, whose area grows with the square of the radius. So the same field lines are diluted over a larger area as distance increases, weakening the field with the square of the distance. Doubling the distance quarters the field strength.
What direction does the electric field point?
The electric field points radially away from a positive charge and radially toward a negative charge. This calculator gives the magnitude of the field; the direction depends on the sign of the charge. A positive test charge placed in the field would be pushed along the field direction, and a negative one against it.
What is Coulomb's constant?
Coulomb's constant, about 8.99 billion newton-meters squared per coulomb squared, is the proportionality constant in the equations for the electric field and force between charges. It sets the strength of the electrostatic interaction. The large value reflects that electric forces are extremely strong compared with gravity for a given amount of charge.