Background: The peak oxygen uptake (VO 2peak) test is the gold standard for cardiorespiratory fitness. However, the test is demanding, requiring sophisticated apparatus for measuring the oxygen uptake. Peak work rate (WRpeak) testing is a promising substitute for peak VO 2peak testing. However, there is a paucity of research conducted to determine reference values (RVs) for WRpeak. Methods: The database from the LowLands fitness registry was used, containing data from health checks from apparently healthy subjects among various professions. Exercise tests were performed using a cycle ergometer and a calibrated metabolic cart. Analysis was executed on 3463 subjects, 2868 male and 595 female. Reference values with corresponding centiles were developed using the LMS method. Results: VO 2peak and WRpeak where highly associated with Pearson's correlation of 0.9 ( p = .001). Weight, height, maximum heart rate, and the respiratory exchange ratio had a positive significant effect ( p < .001) on WRpeak, and age a negative significant effect, in both males and females. The following formulas were computed for RVs: W R p e a k = - 102 + ( 1.5 * w e i g h t [ k g ] ) + ( 1.9 * h e i g h t [ c m ] ) - ( 2.0 * a g e ) - ( s e x * 60 [ M : 0 ; V : 1 ] ) W R p e a k / k g = 2.45 - ( 0.026 * w e i g h t [ k g ] ) + ( 0.024 * h e i g h t [ c m ] ) - ( 0.024 * a g e ) - ( s e x * 0.84 [ M : 0 ; V : 1 ] ) Conclusions: WRpeak can be used as a substitute for VO 2peak when a respiratory gas-analysis system is not available. This study provides RVs for WRpeak and WRpeak/kg in a healthy Dutch/Flemish adult population using cycle ergometry. Further research is needed to obtain RVs for elderly subjects, specific diseases, ethnicities and ergometers.