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Enter the inductance of each inductor in parallel. Add more inductors with the button below. The total inductance is calculated from all filled fields.
When inductors are connected in parallel, the total inductance is found from the sum of reciprocals: \[ \frac{1}{L_{\text{total}}} = \frac{1}{L_1} + \frac{1}{L_2} + \cdots + \frac{1}{L_n} \] For two inductors this simplifies to the product-over-sum form: \[ L_{\text{total}} = \frac{L_1 \cdot L_2}{L_1 + L_2} \] The result is always smaller than the smallest individual inductor in the group. This is the opposite of capacitors in parallel, where values add directly, and it mirrors exactly how resistors in parallel behave.
The derivation follows from Kirchhoff's current law. All inductors in parallel share the same voltage \( V \) across their terminals, so the current through each one is: \[ I_k = \frac{1}{L_k} \int V \, dt \] The total current is the sum of all branch currents: \[ I_{\text{total}} = \sum_k I_k = \left(\sum_k \frac{1}{L_k}\right) \int V \, dt \] Since \( L_{\text{total}} \) is defined by \( I_{\text{total}} = \frac{1}{L_{\text{total}}} \int V \, dt \), we get the reciprocal sum formula directly.
Note on mutual coupling: the formula above assumes no magnetic coupling between the inductors (\( M = 0 \)). If the inductors are physically close together their magnetic fields interact, and the effective inductance will differ from the calculated value. In most practical layouts with separate, shielded components the coupling is negligible, but it is worth keeping in mind when placing inductors near each other on a board.
Parallel combinations of inductors are less common than series combinations, but there are two situations where they appear. The first is handling higher current: placing two identical inductors in parallel halves the effective inductance but also halves the current through each component, which allows the combination to carry twice the current within each inductor's rating. The winding resistance (DCR) also halves, reducing copper losses at high current.
The second situation is reaching a non-standard inductance value. If the target inductance is not available as a single component, two parallel inductors can sometimes hit it more closely than a series pair, particularly when the target is well below typical catalogue values. For reaching a higher inductance from available parts, the inductors in series calculator is usually the better starting point.
Once the equivalent inductance is known, it can be used directly in the RL time constant calculator, the inductor impedance calculator, or the LC resonance frequency calculator.
More calculators: blog.hirnschall.net/tools/.
