A method produces a void fraction (VF) error curve which correlates an apparent VF with the actual VF of a multi-phase flow, the method comprising (a) using a device to measure a property of the multi-phase flow from which an apparent VF may be calculated; (b) calculating the apparent VF using the measured property from the device; (c) determining the actual VF of the multiphase flow using a radiometric densitometer; (d) using the values from steps (b) and (c) to calculate the VF error; (e) repeating steps (b) through (d) for all expected flow conditions to generate a VF error curve.