A calibration-free method for extraction of electromagnetic properties of magnetically coupled anisotropic biaxial metamaterial (MM) slabs from waveguide measurements is proposed. It relies on three measurement steps (thru, empty line, and the same line arbitrarily loaded by the MM slab) to extract electromagnetic properties. It is evaluated against another calibration-dependent method for retrieval of electromagnetic properties of a MM slab constructed by C-shaped resonators. From evaluation analysis, we note that our method, as compared to the calibration-dependent method, not only accurately extracts electromagnetic properties without requiring the use of expensive calibration standards but also is reference-invariant. Published by AIP Publishing.