In this study new metrics were developed for assessing the performance of surgical knots. By adding sensors to a knot tying simulator we were able to measure the forces used while performing this basic and essential skill. Data were collected for both superficial tying and deep tying of square knots using the one hand and two hands techniques. Participants used significantly more force when tying a deep knot compared to a superficial knot (3.79N and 1.6N respectively). Different patterns for upward and downward forces were identified and showed that although most of the time upward forces are used (72% of the time), the downward forces are just as large. These data can be crucial for improving the safeness of knot tying. Combing these metrics with known metrics based on knot tensiometry and motion data may help provide feedback and objective assessment of knot tying skills.