Calories & Hydration Calculator
How much energy, water and food will your body actually burn on this hike? Enter your profile, activity and conditions — get kcal, litres, grams and sodium guidance with the formulas shown.
Your hike profile
BMR from Mifflin-St Jeor, burn from Compendium MET values, water from weather and load. Try the example first.
Results
How is this calculated?
Basal Metabolic Rate (Mifflin-St Jeor, 1990):
Men: BMR = 10×weight(kg) + 6.25×height(cm) − 5×age(y) + 5
Women: BMR = 10×weight(kg) + 6.25×height(cm) − 5×age(y) − 161
Hike energy burn:
kcal = MET × 3.5 × body_weight(kg) / 200 × minutes
The constant 3.5 is resting oxygen uptake (ml/kg/min); /200 converts to kcal/min. MET values come from the Compendium of Physical Activities.
Total daily energy:
Total = BMR × 1.2 (sedentary baseline) + hike_burn
The 1.2 factor covers non-hike activity on a restful day; on a thru-hike, multiply by 1.4–1.5.
Water needs (ACSM-style heuristic):
ml/h = clamp( (400 + max(0,T−15)×30 + max(0,load−5)×10) × intensity × hotFactor, 250, 1500 )
Total water = ml/h × hours + 500 ml
Intensity factor: light 1.0, moderate 1.25, heavy 1.5. Hot/exposed: ×1.10. Clamped to a sensible 250–1500 ml/h range.
Food weight:
food_g = total_kcal / (kcal_per_100g / 100)
Electrolytes:
sweat_L ≈ water_L × 0.8 ; sodium_mg ≈ sweat_L × (500–700 mg/L)
Sources: Compendium of Physical Activities (MET values); Mifflin-St Jeor equation (1990); USDA food composition data; ACSM position stand on exercise fluid replacement. Estimates only — individual sweat rates vary widely, weigh yourself before/after a training hike to calibrate.