basic

Ampère's Law Magnetic Field Around an Infinite Wire Calculator

B = μ₀ · I / (2 · π · r) — perpendicular distance from wire.

Compute the magnitude of the magnetic field a distance r from an infinitely long straight current-carrying wire using Ampère's law: B = μ₀ · I / (2 π r), where μ₀ = 4π × 10⁻⁷ T·m/A. Field circles the wire (right-hand rule) and falls off inversely with distance.

Dr. Helena Ortiz By Dr. Helena Ortiz
Published Last reviewed 1 min read

Inputs

A
m

Results

Enter values and click Calculate to see results.
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How to use this calculator

  1. Fill in the inputs above using the units you already have.
  2. Values update automatically as you type — no submit button needed.
  3. Hover any result row for the underlying formula and intermediate values.

Formula

B = μ₀ · I / (2 π r).

In depth

Compute the magnitude of the magnetic field a distance r from an infinitely long straight current-carrying wire using Ampère's law: B = μ₀ · I / (2 π r), where μ₀ = 4π × 10⁻⁷ T·m/A. Field circles the wire (right-hand rule) and falls off inversely with distance.