An effective approach to design an ultracompact metamaterial absorber is presented. The unit cell of the designed absorber is a three-dimensional square frame constructed in FR4 dielectric layer, which can be counted as a combiner of two pairs of interperpendicular split-ring resonators. Its design is detailed in this study, and an equivalent circuit model analysis is presented to provide an insightful design procedure for the compactness in size. Numerical simulations, together with one experimental result, are presented to verify the design. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:1438–1441, 2015