The invention relates to a method in the check weighing of a weighing system. In the method, a hoist (15) equipped with a weighing system (14) is used to lift a load (27), which is weighed, and the value measured by the weighing system (14) is recorded. In the method, the weighing system (14) is adjusted as required, on the basis of the recorded values. A real load (28), which is weighed when not moving, is used as the load (27). The same real load (28) is also weighed during a normal movement while moving. A reference value is defined from these two weighings of the same real load (28), on the basis of which the weighing system (14) is adjusted if necessary and/or the precision probably achieved by the weighing system (14) is estimated. The invention also relates to a software product and an arrangement in the check weighing of a weighing system, and materials handling equipment.