This study uses a new approach to assign individual marks from a team mark using individual contributions to a teamwork product. A team member's contribution to a teamwork product, in the form of an individual weighting factor, is calculated using team members' co-assessment. A comparison of the proposed approach with existing methods has been discussed with the help of a typical teamwork example. The approach has been refined to make it applicable for the Australian grading system at universities. It has been implemented in a large undergraduate engineering course to observe its effectiveness in practice. The results show that the method encourages teamwork, penalises below-average contributions and rewards above-average contributions. An analysis of a students' perception survey shows that students prefer the approach over alternative approaches. (Contains 1 table and 4 figures.)