MAXScanner calculator widget

RC Time Constant Calculator — Solve τ, R or C + Cutoff & Timing

Editable live calculator

Change any input — the result updates immediately

No hidden assumptions. Inputs, units and the working stay visible so you can check the calculation.

Solve for Resistance Resistance unit Capacitance Capacitance unit Charge target (%) Must be greater than 0 and below 100.Remaining charge during discharge (%) Must be greater than 0 and below 100.

Calculated result

τ = 1,000 ms

Solved RC set: 10 kΩ · 100 µF · τ 1,000 ms

5τ settling reference: 5 s · ideal charge ≈ 99.326%

First-order cutoff: 0.159155 Hz

Time to 90% charge: 2.302585 s

Time to 10% remaining on discharge: 2.302585 s

Charge reference: 1τ 63.212% · 3τ 95.021% · 5τ 99.326%

Show the working

1. τ = 10 kΩ × 100 µF = 1,000 ms.
2. fc = 1 ÷ (2π × 1 s) = 0.159154943 Hz.
3. Charge target time = −τ ln(1 − 0.9) = 2.302585093 s.
4. Discharge target time = −τ ln(0.1) = 2.302585093 s.

Ideal first-order RC model. Component tolerance, leakage, ESR, source impedance and connected load can shift real timing.

Shared links reopen these inputs; saved calculations stay in this browser unless you clear site data.