RC Time Constant Calculator — τ = RC

The time constant τ is the time to charge to ~63% (or discharge to ~37%). After 5τ the capacitor is essentially fully charged.

$\tau = RC$

Solve for

Resistance (R)

Unit

Capacitance (C)

Unit

Result unit

How to interpret the result

A 10 kΩ resistor with a 100 µF capacitor gives τ = 1 s — camera flashes and timing circuits are designed around exactly this product.