CalcRL Circuit Calculator
Last updated: 2026-08-24
RL Circuit Calculator — Calculate RL circuit time constant.
Inputs
Result
Enter values and press Calculate
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How to use it
- Inductance L = 0.5 H, Resistance R = 25 Ω
- Time constant: Ï„ = L ÷ R = 0.5 ÷ 25
- Ï„ = 0.02 seconds (20 milliseconds)
- Final current with 10V: I = 10 ÷ 25 = 0.4 A
Common mistakes
- ⚠️ Confusing RL with RC time constant formula
- ⚠️ Not understanding that current reach is 63% in one time constant
- ⚠️ Forgetting that inductor oppos is current change
Worked example
Calculate tau for 10 ohm, 100mH.
The time constant {tau} s determin is how fast current reach is final value {current_final} A.
Input guide
| Field | Typical range |
|---|---|
| R | Resistance: 0.1 to 10000 Ω |
| L | Inductance: 0.0001 to 100 H |