Abstract: This invention relates to an improved apparatus for measuring the weight of an object being carried by a fork lift truck. Accurate weight is obtained by combining the measurements of the tension load(s) exerted by the chain(s) used to lift and support the fork carrying carriage with a measurement of the vertical forces imposed on the carriage by the mast through the carriage guides that are used to contain carriage movement within the mast and support the moment created by the object being weighed. The weight thusly determined can be easily calibrated for both pitch and roll mast angles. The apparatus can be integrated into the mast system of the fork truck without significantly affecting the fork truck's load carrying capacity. Specifically, the scale apparatus does not increase the overturning moment created by the weight of the object as compared with that of the standard non-instrumented carriage.