Easiest is to use Poser's measurement tool. The measurements returned are based on 1 Poser Native Unit(PNU) is 8.6 ft., so about 2.62 m. For some reason many models available are made assuming 1 unit is 8ft. This explains the confusion. For older Poser versions that do not have the measurement tool load the simple square from props. It has a size of 1ft. Y-scale and x-scale it to measure. For accuracy you can give it a checkboard texture with 0.1 or 0.0825 tile size. Alternatively Google a scale and add it as texture. You can calibrate by moving the prop up and down.