RC Time Constant Calculator

Enter resistance and capacitance to calculate tau, 50/90/99 percent timing, and the ideal RC corner frequency.

Resistance

Capacitance

—Time constant τ = RC

—50% time

—90% time

—99% time

—1/(2πRC)

Educational / low-voltage electronics calculator. Real components have tolerances and non-ideal behavior. Do not use this page as a substitute for qualified design or safety guidance for mains/high-energy electrical systems.

How to use this RC Time Constant Calculator

Calculate RC time constant, common charge timing points, and cutoff frequency. Enter your values above and the result is calculated directly in your browser. No account is required.

Fast answer, clear inputs

This tool is built around one job: give the answer quickly without forcing a signup or hiding the result. Related tools are linked nearby when the next calculation or conversion is useful.