Calculate
Formula and method
Cutoff fc = 1 / (2πRC). Low-pass magnitude = 1 / √(1 + (f/fc)²). High-pass magnitude = (f/fc) / √(1 + (f/fc)²). Gain in dB = 20 log10(magnitude).
Worked example
With R = 1 kΩ and C = 100 nF, cutoff is about 1,591.5494 Hz. At cutoff, either ideal first-order mode has magnitude about 0.7071 (−3.0103 dB).
Limits and safety
Ideal passive first-order response only. Component tolerances, parasitics, source/load impedance, active stages, and high-frequency effects are not modeled.
Privacy
The calculation runs locally. Entered circuit values are not submitted to a server or included in analytics events.