RC Charging and Discharging Calculator
Calculate capacitor voltage, current and stored energy during an ideal RC transition, or solve the time needed to reach an entered target voltage.
YOUR CALCULATION
Result
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Calculation steps
Work through one step at a time or reveal the complete calculation. The steps use your current inputs.
How to calculate
Multiply resistance by capacitance for the time constant. Apply the exponential step response between the entered initial and final voltages. Invert the response logarithm for a reachable target, treating the final asymptote separately.
τ=RC; V(t)=Vfinal+(Vinitial−Vfinal)e^(−t/τ); I(t)=(Vfinal−Vinitial)e^(−t/τ)/R
Worked example
10 kohm and 100 μF give τ=1 s. From 0 V toward 5 V, the capacitor reaches 3.16060279 V after 1 s. Reaching 4 V takes ln(5)=1.60943791 s; reaching exactly 5 V requires an infinite ideal time.
Assumptions and input details
Ideal constant R, C and source voltage; capacitor leakage, equivalent series resistance, inductance and component ratings are excluded. Initial and final voltages may be signed. Current is positive in the direction charging toward the entered source and negative for a lower final voltage. Targets must lie between the endpoints. The exact final value is approached asymptotically; if initial and final are already equal, that same target is reached at time zero. Charge uses Q=CV and energy uses E=CV²/2. The curve shows the first five time constants and does not imply the capacitor is completely settled at five.
References: Analog Devices RC transient response
Unit definitions
Unit selection is independent of language. Each selector contains only units for its physical quantity. Calculations use defined base units internally.
SI prefixes are explicit: for example, milli means one thousandth, micro one millionth and kilo one thousand. Changing a unit changes the interpretation of the entered number.
Using this calculator
Can I enter my own problem?
Yes. Replace the example values with your own inputs. The result, calculation steps, tables and applicable diagrams update from those inputs. Blank or invalid values clear the result; example values are never silently substituted for missing inputs.
Are the results exact?
Results use floating-point arithmetic and displayed rounding. Read the formula, assumptions and any stated data precision before interpreting the result.
Is my input uploaded?
The calculation runs in your browser. No account, file upload or external AI service is required. Inputs are not saved between page reloads.
Calculate the equivalent capacitance of 2–20 capacitors in series or parallel. Enter supply voltage for ideal charge, per-capacitor voltage and stored energy.
Find the equivalent resistance of 2–20 ideal resistors in series or parallel. Enter a DC voltage to calculate current, voltage drop and power for every resistor.
Apply an entered constant growth or decay rate to an initial quantity. Compare periodic and continuous models, view a time curve and find doubling time or half-life.
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