Definition 

Defined as perseverance and passion for long-term goals, Duckworth et al (2007) argue that grit is one of the noncognitive skills that explain differences in attainment between individuals with otherwise equal intelligence. Empirical studies show that while grit is correlated with other personality traits which form the Big Five, it helps to explain differences in outcomes (e.g. test scores) between individuals beyond the effect of either IQ or personality. Grit is particularly important to achievement of difficult goals, which require not only talent but also the sustained and focused application of talent over time (Duckworth et al., 2007).

Measurement Tool 

The leading researcher focusing on grit, Angela Duckworth, provides a set of GRIT scales varying in length: the short (8-item), medium (10-item), and long (12-item). These scales can be used in a large variety of contexts, as items do not pertain to a particular life domain.

• More info on 8-item can be found here
• More info on 10-item can be found here
• More info on 12-item can be found here

References 

Duckworth, A. L., Peterson, C., Matthews, M. D., & Kelly, D. R. (2007). Grit: Perseverance and Passion for Long-Term Goals. Journal of Personality and Social Psychology, 92(6), 1087.

Duckworth, A. L., & Quinn, P. D. (2009). Development and Validation of the Short Grit Scale (GRIT–S). Journal of Personality Assessment, 91(2), 166-174.