SnapCalorieBurn — free MET-based calorie calculators
Estimate rucking calories by body weight, backpack load, speed and time. Compare unloaded walking with gross and active estimates using the LCDA model.
This rucking calorie calculator uses the Load Carriage Decision Aid (LCDA) backpacking equation from Looney et al. (2022), not a fixed activity MET or a percentage added to ordinary walking calories. The model estimates steady-state metabolic power from body mass, walking speed and backpack load relative to body mass. It is designed here for walking with a backpack on level, firm ground. It does not estimate running, hills, soft sand, uneven trails or weighted-vest workouts.
Enter your body weight separately from the loaded backpack. Backpack weight includes the pack itself and everything inside it. Adding the two weights together in the body-weight field would change the equation incorrectly. The load ratio L is backpack mass divided by body mass, with both in the same units. A 20 kg pack for an 80 kg person gives L = 0.25, not 25. Walking speed S is in meters per second: divide km/h by 3.6, or multiply mph by 1.609344 before converting.
M (W/kg) = Mrest + (0.19 + 1.78 × S^0.58 + 0.27 × S^4) × (1 + 1.96 × L^1.36)
This is equation 2 of the source paper. Power is normalized to body mass, not body-plus-backpack mass. The resting term is added after the walking and load terms are multiplied; the backpack multiplier does not multiply resting metabolism. Because the load response is nonlinear, doubling backpack weight does not simply double the calorie cost of carrying it.
Gross calories include both the predicted walking cost and the assumed energy you would expend at rest during that time. Active calories are the estimated walking cost above that resting assumption. They are not a direct measurement, not the total minus an arbitrary percentage, and not a guarantee that a wearable will display the same number. Unlike the site's conventional MET calculator, this page does not subtract a generic 1-MET term: it uses the resting rate entered for this LCDA calculation.
The default resting rate is explicitly assumed to be 1,840 kcal per day, the value used in the worked example. It is not inferred from body weight, age or sex, and is not a claim about your personal metabolism. The paper estimated resting metabolism with the Cunningham equation using DXA-measured lean body mass; this tool instead exposes the daily resting assumption directly. Replace it with a suitable measured or estimated resting daily energy rate if available. Do not enter total daily energy expenditure, which already includes movement. The BMR calculator can provide a separate resting estimate, but an estimated BMR is still not a measured resting metabolic rate.
For a daily resting value R and body mass B, Mrest = R × 4,184 ÷ (86,400 × B) W/kg. One watt is one joule per second and one kcal is 4,184 joules. Gross session kcal = M × B × minutes × 60 ÷ 4,184. Active session kcal uses M − Mrest in the same conversion. Session totals are rounded once to whole kcal; separately rounded displayed figures can differ by one kcal when subtracted.
For 80 kg body weight, a 20 kg backpack, 3.6 km/h (1 m/s) and 60 minutes, using 1,840 kcal/day at rest, the walking term before the load multiplier is 0.19 + 1.78 + 0.27 = 2.24 W/kg. The pack-to-body ratio is 0.25. After applying the load term, the active power is approximately 2.9064 W/kg. This gives approximately 277 gross kcal and 200 active kcal, with 77 resting kcal included in the gross total.
The distance is 3.6 km. With the pack set to zero and all other inputs unchanged, this same model estimates 231 gross kcal and 154 active kcal. The additional pack contribution is approximately 46 kcal. This is a controlled comparison inside one equation, not a comparison with a different MET-based walking estimate. Changing the resting assumption changes both gross totals equally and leaves the active cost and pack contribution unchanged.
Calories per hour are the model's unrounded rate expressed over 60 minutes, not a rounded session total multiplied back up. Distance is speed times time; it does not include elevation gain or account for interruptions. For sessions that change pace or load, estimate each constant segment separately. Extending a steady-state rate over a long session assumes the same walking conditions persist; it does not model fatigue or prove validation for that entire duration.
The development study involved 30 healthy, physically active military-age adults, including 27 men and 3 women, with experience carrying heavy loads. They walked on a level treadmill in combat boots with military backpacks. Loads included 0%, 22%, 44% and 66% of body mass, and walking speeds spanned approximately 0.45–1.97 m/s. The authors also evaluated the equation against seven independent historical datasets involving soldiers and civilians. That is evidence for a specific load-carriage model, not universal accuracy for every person or every outdoor workout.
This tool accepts 1.62–7.092 km/h and backpack mass from zero through 66% of body mass. A conservative body-weight range of 48–120 kg follows the range reported for the external validation participants. The 1–480 minute duration and 500–4,000 kcal/day resting limits are input safeguards, not study-derived training or physiological recommendations. Out-of-range entries receive an explanation rather than an extrapolated calorie figure.
Not every combination of highest speed and heaviest pack was tested in every participant: achievable walking speed decreased with load. These endpoints are research boundaries, not safe or recommended workout targets. Individual results may vary substantially with gait, fitness, footwear, pack placement and environment. The equation does not justify a universal error percentage. Weighted vests distribute mass differently and are not validated by this backpack implementation. Hills and difficult terrain need their own supported model rather than an invented correction.
It depends on body weight, backpack weight, walking speed, duration and the assumed resting rate. At 80 kg body weight, 20 kg backpack, 3.6 km/h and 60 minutes, with 1,840 kcal/day assumed at rest, this LCDA model estimates 277 gross kcal and 200 active kcal above rest.
No. This implementation is limited to backpack walking on level, firm surfaces. It does not validate weighted vests, running, uphill or downhill routes, or rough terrain. Do not add pack weight to body weight or substitute a vest weight to bypass that scope.
LCDA adds resting metabolic power to the estimated walking cost. The default 1,840 kcal/day is an explicit example assumption, not a personal measurement or a value inferred from your body weight. You can replace it with an appropriate measured or estimated resting rate, not total daily calories.
No. It is the upper load ratio investigated in the development study, not a training recommendation or a safety limit. Not every combination of maximum speed and maximum load was tested in every participant.
Looney et al. (2022): Modeling the Metabolic Costs of Heavy Military Backpacking, Medicine & Science in Sports & Exercise, 54(4), 646–654. Equation 2 supplies the coefficients; the methods and external-validation sections supply the population and experimental scope.
For walking without a backpack, see the walking calorie calculator. For unladen treadmill incline walking, use the separate incline walking calculator; do not combine its incline term with this backpack formula. The MET calculator uses a different, explicitly explained activity-based method.