RcTau · electrical

RcTau rc time constant

Know τ and ~5τ before picking resistor/capacitor values for a timing screen

TECHNICAL UTILITY · RC_TIME_CONSTANT

Result

Enter values to begin.

τ = R·C; five_τ = 5·R·C

How to use this estimate

Compute RC time constant τ=RC and the approximate 5τ settling time. How it works: τ = R·C; five_τ = 5·R·C. Out of scope: active filters; ESR/ESL; op-amp compensation; PCB parasitics. This is an approximate screening estimate, not a substitute for manufacturer charts or a full engineering design. Does not certify code compliance; confirm manufacturer data where it applies.

Sources, methodology, and assumptions

Methodology

τ = R·C; five_τ = 5·R·C

Assumptions

Lumped R and C; Step response context. This is an approximate screening estimate, not a substitute for manufacturer charts or a full engineering design.

Out of scope

active filters; ESR/ESL; op-amp compensation; PCB parasitics

Sources

NIST SP 811 — unit consistency context (not exact formula page) — NIST
NIST SI electrical units — NIST

Last technically reviewed: 2026-09-11