All three expressions are accurate, with typical errors of 2 – 3%, and very simple, and are therefore excellent candidates for use in design and synthesis. The thickness of the inductor has only a very small effect on inductance and will therefore be ignored.

**Notes**:

Fill in appropriate values in the first four fields. Then push “calculate”.

**1μm = 0.001mm**

**1μm = 0.00003937007874015748 inch**

**Reference:**

S.S. Mohan, M. Hershenson, S.P. Boyd and T.H. Lee

Simple Accurate Expressions for Planar Spiral Inductances

*IEEE Journal of Solid-State Circuits*, Oct. 1999, pp. 1419-24.

For multilayer spiral pcb coils see here:

A new calculation for designing multilayer planar spiral inductors