RL Filter Cutoff Calculator Formula

Understand the math behind the rl filter cutoff calculator. Each variable explained with a worked example.

Use the RL Filter Cutoff Calculator

Formulas Used

Cutoff Frequency

cutoff_hz = resistance / (2 * pi * l_h)

Time Constant (L/R)

time_constant = l_h / resistance * 1000

Variables

VariableDescriptionDefault
resistanceResistance(Ω)1000
inductance_mhInductance(mH)10
l_hDerived value= inductance_mh / 1000calculated

How It Works

RL Filter Cutoff

f_c = R / (2 x pi x L)

Time constant tau = L/R. An RL low-pass passes DC and attenuates high frequencies.

Worked Example

R = 1k, L = 10 mH.

resistance = 1000inductance_mh = 10
  1. 01L = 0.01 H
  2. 02f_c = 1000 / (2pi x 0.01) = 15,915.5 Hz
  3. 03tau = 0.01 / 1000 = 0.01 ms

Ready to run the numbers?

Open RL Filter Cutoff Calculator