Enter your Resistance (R), Capacitance (C), Input Voltage (V), and Time (t) into the RC Circuit Calculator to find your circuit's Time Constant (τ), along with Voltage at Time t, Cutoff Frequency, Energy Stored, and how far along the capacitor is as a Percentage of Final Value.
Time Constant (τ)
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Voltage at Time t
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Cutoff Frequency
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Energy Stored
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Percentage of Final Value
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An RC circuit is a fundamental electrical circuit consisting of a resistor (R) and capacitor (C) connected in series. It's characterized by its ability to store energy and filter signals based on frequency.
The time constant τ = RC determines charging time. The capacitor reaches 63.2% of final voltage in one time constant, 95% in 3τ, and is considered fully charged (99.3%) in 5τ.
Not exactly. The time constant τ = RC is the time to reach 63.2% of final voltage. Full charging time is typically considered 5τ, when the capacitor reaches 99.3% of final voltage.
Yes, the cutoff frequency fc = 1/(2πRC) is the frequency at which the output is -3dB (70.7%) of the input. This determines the filter characteristics of the RC circuit.
Charging occurs when voltage is applied to an uncharged capacitor, following V(t) = V₀(1-e^(-t/τ)). Discharging happens when a charged capacitor releases energy, following V(t) = V₀e^(-t/τ).
RC circuits can act as low-pass or high-pass filters. Taking output across the capacitor creates a low-pass filter, while taking output across the resistor creates a high-pass filter.
Use consistent units: resistance in ohms (Ω), capacitance in farads (F), time in seconds (s), and voltage in volts (V). The calculator handles unit prefixes automatically.
Energy stored in a capacitor is E = ½CV², where C is capacitance and V is the voltage across the capacitor. This energy is released during discharge through the resistor.