Background At the interface of the occupational setting and rehabilitation, normative values for functional ability are desirable and worthwhile. The Norwegian Function Assessment Scale (NFAS) is a 39 item self-report instrument based on the International Classification of Functioning, Disability and Health (ICF). As the questionnaire was not used in a working population, we aimed to obtain functional levels of employees in Germany as measured through the NFAS. Methods The NFAS was included in the Study on Mental Health at Work (S-MGA) 2011/12, a representative German survey of employees aged 31 to 60 years. For descriptive analyses, 95% confidence intervals were applied through bootstrap estimation to the skewed data of the NFAS (range from 1 = ‘no difficulty’ to 5 = ‘could not do it’). The data were analysed by age decades, professional qualification, and by disabilities, congenital diseases and accidents, stratified by sex. Linear regression analyses were conducted to estimate adjusted effects of age, professional qualification, and health limitations. Results The NFAS total score was 1.17 (95% CI = 1.15–1.17). Thirty-five percent of the employees’ (1378 out of 3937 participants) reported the best possible functional ability (NFAS total score of 1.00). Managing and walking/standing were the NFAS’ most affected domains with a score of 1.26 (95% CI = 1.23–1.27), respectively. The regression analysis confirmed more functional difficulties for elder employees, females, employees with low professional qualification, and for employees suffering from disability and accidents. Conclusions The study presents normative values of functional ability for the workforce. The results are useful for score interpretation in rehabilitation and return-to-work processes. Electronic supplementary material The online version of this article (10.1186/s12995-017-0183-4) contains supplementary material, which is available to authorized users.