The System Usability Scale (SUS) has long been assumed to be unidimensional, but recent factor analysis of two independent data sets reveals it actually has two factors: Usable (8 items) and Learnable (2 items, Items 4 and 10). These scales have reasonable reliability (coefficient alpha of .91 and .70, respectively) and correlate highly with the overall SUS (r = .985 and .784, respectively). They also correlate significantly with each other (r = .664), but at a low enough level to be used as separate scales. A sensitivity analysis showed a significant Test by Scale interaction, indicating the differential utility of the new scales. Practitioners can continue using the current SUS but also benefit from the new scales to extract additional information. The data support using “awkward” rather than “cumbersome” in Item 8. The SUS was developed in 1986 by John Brooke and consists of 10 items. It has been widely used for assessing usability, with a reliability of .85 in early studies and .91 in more recent ones. The SUS has been shown to have good reliability and validity, with a strong correlation between the SUS and other measures of usability. However, factor analysis suggests the SUS has two underlying factors: Usable and Learnable. The Usable scale includes 8 items, while the Learnable scale includes 2 items. Both scales have high reliability and correlate strongly with the overall SUS. The two scales also correlate significantly with each other, but at a low enough level to be used separately. The sensitivity analysis showed that the two scales provide different information, with the Usable scale being more sensitive to changes in usability and the Learnable scale being more sensitive to changes in learnability. The results suggest that the SUS can be decomposed into two separate scales, each providing unique information about usability and learnability. The data also show that the central tendency of the SUS scores differs between two data sets, suggesting that the two datasets may represent different types of users and products. The findings support the use of “awkward” rather than “cumbersome” in Item 8. The study also highlights the importance of item wording in ensuring the reliability and validity of the SUS.The System Usability Scale (SUS) has long been assumed to be unidimensional, but recent factor analysis of two independent data sets reveals it actually has two factors: Usable (8 items) and Learnable (2 items, Items 4 and 10). These scales have reasonable reliability (coefficient alpha of .91 and .70, respectively) and correlate highly with the overall SUS (r = .985 and .784, respectively). They also correlate significantly with each other (r = .664), but at a low enough level to be used as separate scales. A sensitivity analysis showed a significant Test by Scale interaction, indicating the differential utility of the new scales. Practitioners can continue using the current SUS but also benefit from the new scales to extract additional information. The data support using “awkward” rather than “cumbersome” in Item 8. The SUS was developed in 1986 by John Brooke and consists of 10 items. It has been widely used for assessing usability, with a reliability of .85 in early studies and .91 in more recent ones. The SUS has been shown to have good reliability and validity, with a strong correlation between the SUS and other measures of usability. However, factor analysis suggests the SUS has two underlying factors: Usable and Learnable. The Usable scale includes 8 items, while the Learnable scale includes 2 items. Both scales have high reliability and correlate strongly with the overall SUS. The two scales also correlate significantly with each other, but at a low enough level to be used separately. The sensitivity analysis showed that the two scales provide different information, with the Usable scale being more sensitive to changes in usability and the Learnable scale being more sensitive to changes in learnability. The results suggest that the SUS can be decomposed into two separate scales, each providing unique information about usability and learnability. The data also show that the central tendency of the SUS scores differs between two data sets, suggesting that the two datasets may represent different types of users and products. The findings support the use of “awkward” rather than “cumbersome” in Item 8. The study also highlights the importance of item wording in ensuring the reliability and validity of the SUS.