This paper deals with the design, analysis and experimental characterization of a planar inductor realized on FR4-PCB (Printed Circuit Board) for a DC-DC converter equipped with GaN (Gallium Nitride) based power devices. In the past, such inductors were conceived for radio-frequency applications; now, thanks to fast switching frequencies allowed by WBG (Wide BandGap) power devices, they can be considered for power conversion applications. A planar inductor has been designed for a synchronous GaNbased buck converter working at 1 MHz switching frequency; the inductor design starts from the analytical equations describing radiofrequency integrated inductors; then, its performance has been verified firstly by FEM (Finite Element Method) software and then by experimental measurements. Finally, the realized inductor has been tested in different working conditions in the power converter. To highlight the benefits and drawbacks, a comparison with ferrite-based inductors has also been proposed. Planar coreless inductors exhibit constant inductance when the current varies, and their lack of saturation reduces current distortion and harmonic pollution; however, size and weight are larger than with ferrite-based inductors.