Electric Field Calculator
electric field calculator. Get instant, accurate results. Enter values for instant results with step-by-step formulas.
Reviewed for accuracy by Manoj Kumar, Mathematics Educator
Electric Field Calculator
Calculator
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Formula: E = kQ/r² (point charge) | E = V/d (parallel plates)
Worked example — 899,000 N/C
Formula
E = kQ/r² (point charge) | E = V/d (parallel plates)
Electric field strength at a point in space due to a charge or between plates.
Worked Examples
Example 1: Point charge
Problem:Q=1μC at r=0.1m
Solution:E=8.99e9×1e-6/0.01=8.99×10⁵ N/C
Result:899,000 N/C
Frequently Asked Questions
What is an electric field?
An electric field is a region in space where a charged particle experiences a force. For a point charge Q, the field at distance r is E = kQ/r², where k = 8.9875×10⁹ N·m²/C². Between parallel plates with voltage V and separation d, E = V/d. The SI unit of electric field is N/C or equivalently V/m.
How do you calculate electric field strength?
For a point charge: E = kQ/r². For Q = 1 μC at r = 0.1 m: E = 8.9875×10⁹ × 10⁻⁶ / 0.01 = 8.9875×10⁵ N/C. For parallel plates with V = 100 V and d = 0.01 m: E = 100 / 0.01 = 10,000 V/m. The force on a test charge q is F = qE.
What units does the electric field calculator use?
Charge Q is in coulombs (C); use 1e-6 for microcoulombs. Distance r is in meters (m). For the parallel-plate mode, voltage V is in volts (V) and plate separation d in meters (m). Output electric field E is in N/C (= V/m), and electric potential is shown in volts (V).
What is a real-world example of electric field?
The Earth's atmosphere has a fair-weather electric field of about 100 V/m pointing downward. Near a thundercloud, this can exceed 10,000 V/m, strong enough to ionize air and trigger lightning. In electronic capacitors, fields of 10⁶–10⁷ V/m are common within the dielectric layer.
Background & Theory
Electric Field Strength in Context
Electric field (E) describes the force per unit charge at a point in space, and it's what determines how a charged particle placed there would accelerate. The two formulas used by this calculator cover the two situations that come up constantly in intro electromagnetism: a single point charge radiating a field outward (E = kQ/r², following an inverse-square law like gravity), and a parallel-plate capacitor where the field is uniform between the plates (E = V/d).
| Environment | Typical field strength |
|---|---|
| Earth's fair-weather atmospheric field | ~100-150 V/m, pointing downward |
| Beneath a thundercloud before a lightning strike | 10,000+ V/m |
| Dielectric breakdown of dry air | ~3×10⁶ V/m (3 MV/m) — beyond this, air ionizes and sparks |
| Inside a ceramic capacitor's dielectric layer | 10⁶-10⁷ V/m, sustained safely because the dielectric's breakdown strength is much higher than air's |
| Field binding an electron to a hydrogen nucleus (Bohr radius) | ~5×10¹¹ V/m |
Because field strength from a point charge falls off as 1/r², moving twice as far away reduces the field (and the force on any test charge) to one quarter — the same inverse-square relationship that governs gravity and light intensity.
Reviewed for accuracy by Manoj Kumar, Mathematics Educator · Editorial policy
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