RC Time Constant Calculator
Enter the known values and run the calculation.
Enter the resistance in ohms and the capacitance in farads, then run the calculation.
The result reports the RC time constant in seconds.
Overview
Compute RC charging and discharge timing for transient behavior in resistor-capacitor networks.
Use this tool to calculate the first-order time constant of an RC network from its resistance and capacitance.
Use it for charge and discharge timing estimates, filter intuition, and checking whether a transient is fast or slow relative to the rest of the system.
The math and how it's used
Resistance is treated in ohms and capacitance is treated in farads.
The result is the dominant first-order time constant in seconds.
This is the first number most engineers reach for when judging whether an RC node will settle quickly or drift slowly relative to the rest of a design.
It tells you the dominant time scale, not the full transient story. Thresholds, initial conditions, loading, and source impedance still shape the actual waveform.
What to watch
The time constant alone does not define every transient detail. Initial conditions, threshold levels, source impedance, and loading still matter.
Use this as the dominant first-order estimate before moving into full waveform simulation or measured step response.