Backcountry Water and Caloric Requirement
Water (L) and kcal per person per day with trip totals.
Example
You enter
- Body weight (lb) 170
- Ambient band moderate
- Exertion moderate
- Trip days 3
- Group size 1
You get
- Water / person / day 3.50 L
- Kcal / person / day 2,890
- Trip water (group) 10.5 L
- Trip kcal (group) 8,670
No published worked example is on file for this calculation. It is checked against a hand-worked derivation of its method and an independent reference test.
Details, formula, and sources
Formula or tableWater L/day by ambient band (cool 2.0 / moderate 3.5 / hot 5.0 / extreme 6.0) × group_size × days. Kcal/day = a resting (BMR) baseline of 1,500 kcal at 150 lb, scaled with body weight, × an activity factor (easy 1.4 / moderate 1.7 / hard 2.0 / extreme 2.5) × group × days.
Source and editionU.S. Army FM 21-10 (Field Hygiene and Sanitation) + USDA Dietary Reference Intakes by name; ACSM (American College of Sports Medicine) Position Stand on hydration by name.
Free accessUSDA DRI free at nal.usda.gov; ACSM Position Stands free at acsm.org.
What governsGeometry is not forecasting. Avalanche advisory and incident commander govern.
API field namesbody_weight_lb, ambient_band, exertion, trip_days, group_size, water_per_day_l, kcal_per_day, trip_water_l, trip_kcal