RC Time Constant Calculator
Calculate the time constant of a resistor-capacitor circuit (τ = R × C) and the time needed for the capacitor to fully charge.
- Full charge time (5τ)
- 5.0000 s
Formula: τ = R × C
About RC Time Constant Calculator
RC Time Constant Calculator is a free online calculator that gives you an instant, accurate result as you type. Calculate the time constant of a resistor-capacitor circuit (τ = R × C) and the time needed for the capacitor to fully charge.
The calculation uses the standard formula τ = R × C and updates live with every change to the inputs. Everything runs client-side in your browser — fast, private, and free to use as often as you like.
After one time constant a capacitor reaches about 63.2% of full charge; after five time constants it is considered fully charged at over 99%.
Frequently Asked Questions
Is RC Time Constant Calculator free to use?
Yes. RC Time Constant Calculator is completely free, with no sign-up, no downloads, and no usage limits. You can use it as many times as you like on any device with a web browser.
How accurate is this calculator?
The calculator applies the standard formula (τ = R × C) with full floating-point precision and rounds only the displayed result. For most practical purposes the results are exact.
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