Parallel Inductors Calculator - Reciprocal-Sum Equivalent Inductance and Current Split

The parallel inductors calculator reduces a bank of two to ten inductors wired in parallel to a single equivalent inductance and shows how the bank splits current across each coil. Use it when you have several inductors on the same two nodes and need the combined inductance, the reciprocal sum that proves the answer, or each inductor's share of the supply current.

• • Combine a parallel bank into one equivalent: Enter two to ten inductance values and read the single equivalent inductance for the parallel bank in H, mH, uH, or nH.
• • Plan an inductor current divider: Add a total current into the bank and read how it distributes across each inductor.
• • Verify the textbook worked example: Enter the 5 H, 10 H, 15 H parallel bank and read 2.73 H as the combined inductance.
• • Sanity-check a hand calculation: Compare the calculator output against a manual 1/L_eq = sum(1/L_i) computation when teaching circuits labs.

Inductors wired in parallel share the same induced EMF, so the same back-EMF appears across every coil. The total current divides across the bank in inverse proportion to each inductance, which makes the equivalent inductance always smaller than the smallest inductor in the bank. That is the parallel-inductor rule this calculator automates.

Once you have the equivalent parallel inductance, the inductive reactance calculator takes the same henry value alongside a frequency for X_L = 2*pi*f*L.

Once you have the equivalent parallel inductance, the next question is usually how fast that combined inductor resists current changes, and the capacitors in series calculator takes the same reciprocal-sum pattern one step further for the capacitive mirror.

The parallel inductors calculator starts with the self-inductance relation v = L di/dt applied to every coil in the bank. Because the induced EMF is the same across each branch, the di/dt contributions sum and the equivalent inductance falls out as one over the sum of reciprocals.

• L_1, L_2, ..., L_n: Inductance of each inductor in the bank after converting the selected prefix (H, mH, uH, nH) to henries.
• L_eq: Equivalent parallel inductance in henries, equal to one divided by the reciprocal sum of every active inductor.
• I_total: Total current entering the parallel bank. When zero, the calculator hides the per-inductor current split.
• I_i: Current through the i-th inductor. Computed as I_total x L_eq / L_i.

The calculator picks the display unit for the equivalent inductance from the magnitude of the answer, so a bank that resolves to 2.73 H renders as 2.73 H and a bank that resolves to 3.33e-3 H renders as 3.333 mH. Current outputs are hidden when the total current is zero so the form stays useful for inductance-only checks.

For two inductors the same rule simplifies to L_eq = (L_1 x L_2) / (L_1 + L_2), the product-over-sum form that mirrors the two-resistor parallel shortcut.

According to Wikipedia - Series and parallel circuits (Inductors), the equivalent inductance of non-coupled inductors in parallel equals the reciprocal of the sum of reciprocals of the individual inductances, written as L = (1/L_1 + 1/L_2 + ... + 1/L_n)^-1.

As published by Omni Calculator - Inductors in parallel, the parallel formula is derived from di/dt = e/L applied to the same induced EMF across every inductor, which yields 1/L_eq = 1/L_1 + 1/L_2 + ... + 1/L_n.

Once the parallel inductance is in hand, an audio designer usually wants to pair it with a series capacitor on the same node, and the crossover calculator solves for the matching capacitor value at a chosen crossover frequency.

Four concepts make the parallel-inductor rule easier to remember. Once these click, every reciprocal-sum answer reads itself.

The parallel-inductor rule mirrors the parallel-resistor rule and contrasts with the series-inductor rule, which is just a straight sum of inductances.

The parallel-inductor rule mirrors the parallel-resistor rule and contrasts with the series-inductor rule, which is just a straight sum of inductances; the capacitive reactance calculator extends the same reciprocal pattern to AC analysis.

Enter the bank, the unit, and an optional total current. The form rebuilds its inductor fields from the count selector and shows the equivalent inductance, the reciprocal sum, and the per-inductor current split.

1. 1 Choose the number of inductors: Set the count selector between 2 and 10. The form keeps the active rows visible.
2. 2 Pick the inductance unit: Select H, mH, uH, or nH. The same unit is applied to every entry.
3. 3 Enter the inductance values: Fill the active inductor rows. Skip a row by leaving it at 0. At least two rows must hold a positive value.
4. 4 Add an optional total current: Enter the current entering the parallel bank. Leave it at 0 to hide the per-inductor current split.
5. 5 Read the equivalent inductance: Equivalent L is shown in the unit that best matches its magnitude, alongside the reciprocal sum and the smallest inductance as a sanity bound.
6. 6 Review the per-inductor current split: When I_total is positive, the current through each of the first four inductors is shown.

Two 47 mH inductors in parallel with 500 mA entering the bank: enter L_1 = 47, L_2 = 47, unit = mH, I_total = 0.5. The parallel inductors calculator returns 23.5 mH equivalent and 250 mA through each inductor.

Once the equivalent parallel inductance is known, the next step is usually to combine it with a series capacitor for filter timing, and the capacitor charge time calculator reads the RC time constant on the same node so both halves of the filter stage can be planned in one workflow.

Putting the reciprocal-sum rule and the current split behind one form removes the busywork that distracts from circuit design.

• • Combine up to ten inductors in one step: The form takes a bank of two to ten inductors and reduces it to a single henry value.
• • Skip the manual 1/L math: The reciprocal sum and its inverse are computed in one pass, so there is no risk of forgetting to invert the sum.
• • Use any supported prefix as the form unit: The selector converts H, mH, uH, and nH entries to henries before the formula runs.
• • Read the per-inductor current split: Current divider outputs show how the supply current lands on each inductor.
• • Use the smallest inductance as a sanity check: The calculator shows the smallest active inductance so the user can confirm the equivalent is in fact smaller.
• • Pick the right display unit automatically: Equivalent L and smallest L are rendered in the unit that fits the magnitude, so 3.33e-3 H is read directly as 3.333 mH.

Once the equivalent parallel inductance is known, the parallel capacitor calculator is the natural follow-up when the next step is to compare inductive and capacitive parallel banks in a filter design.

The reciprocal-sum rule is exact for non-coupled ideal inductors. Real components add tolerances and parasitic effects that move the answer away from the textbook number.

• • The calculator assumes ideal inductors with stable inductance across the operating current. Iron-core and ferrite-core coils drift with bias and temperature, so the answer is a first-pass estimate.
• • The current split uses the same-EMF rule and assumes the inductors are non-coupled. Real coils pick up mutual inductance M, which can shift the split and the equivalent value.
• • The per-inductor current outputs only cover the first four inductors. Banks longer than four require manual extension using I_i = I_total x L_eq / L_i.

As published by Wikipedia - Inductance, the parallel formula assumes non-coupled inductors, and the equivalent L = (L_1 L_2 - M^2) / (L_1 + L_2 - 2M) is required when the mutual inductance M between coils is non-negligible.

When DC resistance or ESR is non-negligible, the capacitor calculator helps quantify the small leakage path that sits across each branch and shapes the DC bias on the bank.