The evaporative requirement for heat balance determines whole‐body sweat rate during exercise under conditions permitting full evaporation

•  A relative exercise intensity (%) protocol is often used to compare absolute whole‐body sweat rates (WBSRs) during exercise between participants of different aerobic capacity. •  Under conditions permitting full evaporation, heat balance theory suggests that exercise intensity should be fixed to elicit the same rate of evaporation required for heat balance (Ereq). •  Whole‐body direct calorimetry was employed to measure WBSRs throughout 90 min of exercise across a range of air temperatures and rates of metabolic heat production. •  Irrespective of ambient temperature and metabolic heat production, Ereq alone described ∼90% of all variability in WBSR during steady‐state and non‐steady‐state exercise, whereas <2% of variation was independently described by %. •  To perform an unbiased comparison of WBSRs (but not necessarily core temperature) between different individuals/groups under conditions allowing full evaporation, future studies should consider using a fixed Ereq irrespective of the % incurred.