ONE FORMULA, ONE ANSWER
RC Time Constant Calculator
Check the time constant of a first-order charging or filter circuit. Choose input units and calculate one value within the stated conditions.
Inputs
Calculations run in this browser. Scientific notation such as 1.2e-3 is supported. Do not group thousands.
Result
RC time constant τ
Enter values and select Calculate.
τ = R C
Assumptions
Use R,C>0. R is the equivalent resistance seen by the capacitor. This is a single first-order RC model. One time constant is not the time to complete charging.
Displayed values are floating-point approximations. Measurement uncertainty and design safety factors are not calculated.
Formula references and credits
NaNa Lab created the code, descriptions, icons and preview images. Text, figures and code from the linked references have not been reproduced.
Physical constants: NIST / CODATA 2022. The values of μ₀ and ε₀ are measured recommendations, not exact defining constants. Values and precision notes are in the source record.
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