Inductance Calculator

Inductance Formula

Worked Example

A 200-turn air-cored solenoid, 20 mm in diameter and 100 mm long:

1. L = μ₀μᵣN²A ÷ l = 0.000001256637062 × 1 × 200² × 0.0003141592654 m² ÷ 0.1 m
2. L = 0.0001579136705 H = 157.9136705 µH

In henries: 0.0001579136705 H

GATE tip

Magnetic circuits work like Ohm’s law: reluctance ℛ = l/(μ₀μᵣA), flux Φ = NI/ℛ and L = N²/ℛ. An air gap adds its own reluctance in series and usually dominates.

More Electromagnetic Fields Calculators

• Capacitance Calculator

  C = ε₀εᵣA/d

  coax C = 2πε L/ln(b/a); concentric spheres 4πε ab/(b − a); isolated sphere 4πε a

  Example: Two 100 cm² plates 1 mm apart in air: Capacitance C = 88.5419 pF.

  Open the capacitance calculator →

• Magnetic Field Calculator

  B = μ₀I/(2πr) (wire), μ₀NI/(2R) (loop centre), μ₀μᵣNI/l (solenoid)

  toroid B = μ₀μᵣNI/(2πR); H = B/(μ₀μᵣ)

  Example: A long straight wire carrying 10 A, at 1 cm: Magnetic flux density B = 0.2 mT.

  Open the magnetic field calculator →

• Electric Field Calculator

  E = q/(4πε r²), λ/(2πε r), σ/(2ε)

  ε = ε₀εᵣ; potential of a point charge V = q/(4πε r)

  Example: A 1 nC point charge, 1 m away, in air: Electric field |E| = 8.98755 V/m.

  Open the electric field calculator →

• Lorentz Force Calculator

  F = q v B sin θ, F = B I L sin θ

  orbit radius r = mv⊥/(|q|B); cyclotron frequency f = |q|B/(2πm)

  Example: An electron moving at 10⁶ m/s at right angles to a 0.5 T field: Force F = 8.01088 × 10⁻¹⁴ N.

  Open the lorentz force calculator →

Frequently asked questions

Sources

• The International System of Units (SI), 9th edition (SI Brochure), Bureau International des Poids et Mesures .

Last reviewed: 2026-10-15. Factors are stored exactly and computed with 50-digit decimal arithmetic. See how we verify conversion factors.