⚡
Instant result
Enter the data and press the button to do the calculation.
Online Calculator
RC time constant calculator
Enter resistance and capacitance to calculate τ = R × C and charging reference values for an ideal RC circuit.
Information
🔒
Local processing
The values are processed directly in your browser.
💸
Free
No registration, external API or subscription required.
Frequently asked questions
What is the formula of the RC time constant?
τ = R × C.
What percentage does a capacitor reach after 1τ?
Approximately 63.21% of its final value during charging.
What happens at around 5τ?
The ideal charge level exceeds approximately 99.3%.
What units does it use?
Ohms for R and microfarads for C; the result for τ is shown in seconds.