Objectives: The purpose of this study was to examine metabolic effects of soldier performance on a simulated road march, comparing two functionally equivalent military ensembles (FEMEs) with changing gradation of marching, and to create prediction equations addressing workload with different loads and treadmill grades. Methods: Fourteen male military subjects were tested while wearing two different FEMEs on a graded (0%, 5%, or 10%), 3.5 miles/h, road march for 30 minutes. Data collected included oxygen uptake (VO2), carbon dioxide output, ventilation, respiratory exchange ratio, and heart rate (HR). Results: No significant differences were found between the two FEMEs in each graded condition. Combining ensemble data, significant differences occurred in all conditions, comparing all grades. A 10% graded road march (3.5 miles/h, ∼27-kg load) represented 61% to 90% of maximal values. For treadmill grades of <10%, VO2 and HR were modeled as follows (adjusted R 2 = 0.89 [VO2] and 0.82 [HR]): VO2 (mL/kg per minute) = 10 + [2·grade (%)] + [0.2·load (% of body mass)]; HR (beats per minute) = 90 + [6·grade (%)] + [0.7·load (% of body mass)]. Conclusions: Three factors, namely, elevation grade, equipment weight (load), and overall subject physical abilities, were significant for overall metabolic demand during a simulated graded road march and might affect field performance.