Toroid: L = AL × N²
Three modes: L from A_L, find N for target L, or calculate from geometry.
AL Value (nH/turn²)
nH/t²
N Turns
Results
Inductance
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Turns
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AL Value
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Details
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Toroid Inductor Calculator
Core — Toroid ring. Closed magnetic path means minimal leakage and low EMI.
AL — Inductance factor from the core datasheet. nH per turn squared. Depends on core size, material, and any gap.
N — Number of turns wound on the toroid. L scales with N².
AL — Inductance factor from the core datasheet. nH per turn squared. Depends on core size, material, and any gap.
N — Number of turns wound on the toroid. L scales with N².
Toroid Inductor Calculator
A toroid is a ring-shaped core with wire wound around it. The closed magnetic path means virtually all flux stays inside the core — minimal EMI, no shielding needed, and predictable inductance. Most practical toroid designs use the manufacturer's AL value: L = AL × N².
Using the AL Value
L = AL × N²
AL = inductance factor (nH per turn²) from core datasheet
N = number of turns
Example: T50-26 core, AL = 4300, N = 20
L = 4300 × 400 = 1720000 nH = 1.72 mH
AL = inductance factor (nH per turn²) from core datasheet
N = number of turns
Example: T50-26 core, AL = 4300, N = 20
L = 4300 × 400 = 1720000 nH = 1.72 mH
{body_sibs['solenoid-inductance']} {all_sibs['solenoid-inductance'][1]}.
Finding Turns for a Target Inductance
N = √(L / AL)
Target: 1 mH on T50-26 (AL = 4300 nH/t²)
N = √(1000000 / 4300) = √232.6 = 15.3 → 16 turns
Target: 1 mH on T50-26 (AL = 4300 nH/t²)
N = √(1000000 / 4300) = √232.6 = 15.3 → 16 turns
{body_sibs['mutual-inductance']} {all_sibs['mutual-inductance'][1]}.
From Core Geometry
Ae = h × (OD − ID) / 2 — effective area
le = π × (OD + ID) / 2 — mean path length
L = μ₀μrN²Ae / le
le = π × (OD + ID) / 2 — mean path length
L = μ₀μrN²Ae / le
{body_sibs['inductor-energy']} {all_sibs['inductor-energy'][1]}.
Frequently Asked Questions
How does this fit in the inductor calculator family?
Each inductor calculator covers a different aspect: energy storage, current rise, time constant, mutual coupling, load analysis, physical design (solenoid, helical, toroid), and measurement (inductance calculator). Use them together for complete inductor design.
Last updated: March 2026