basic

RC Time Constant Calculator

τ for an RC charging or discharging circuit.

Compute the time constant τ = RC of an RC circuit, plus the practical "5τ" full-charge time.

Daniel Oh By Daniel Oh
Reviewed by Dr. Helena Ortiz
Published Last reviewed 1 min read

Inputs

Ω
F

Results

Enter values and click Calculate to see results.
Was this helpful?

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 = R · C. Capacitor reaches ~63.2% of V_in after τ and ~99.3% after 5τ.

In depth

Compute the time constant τ = RC of an RC circuit, plus the practical "5τ" full-charge time.