basic

RL Time Constant Calculator

τ = L / R for an RL circuit.

Compute the time constant τ = L / R of a series RL circuit, the time to reach 63 % of final current, and the rough cutoff frequency f_c = R / (2π · L).

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

Inputs

H
Ω

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

τ = L / R; f_c = R / (2π · L).

In depth

Compute the time constant τ = L / R of a series RL circuit, the time to reach 63 % of final current, and the rough cutoff frequency f_c = R / (2π · L).