The Pandolf load-carriage equation, in your browser. The same math RuckTrack runs on your watch, whether the weight is a ruck, a loaded pack, or a weighted vest.
Heart rate can't see weight, only strain. Most watches estimate calories from your pulse, which rises under a load but under-counts it, so a ruck reads lower than the work actually cost. This calculator uses the U.S. Army's Pandolf equation instead: body weight, pack weight, speed, grade, and terrain in; metabolic cost out. The loaded and unloaded columns update together so you can see exactly what your pack is worth. The equation doesn't care what you call the weight: ruck plates, a loaded hiking pack, and a weighted vest all count the same.
Mirrors RuckTrack's Manual treadmill mode: incline and belt speed into the full equation, terrain fixed at Road (η = 1.0). The app's Auto mode scales the watch's own heart-rate estimate by pack weight instead, which a browser can't reproduce.
This table is generated live by the same function as the calculator, using your body weight, speed, and grade from above. The pattern worth knowing: the pack bonus scales with the load-to-body-weight ratio. Grade and terrain raise the total burn a lot, but they raise the loaded and unloaded numbers together, so the percentage moves slowly. A heavy pack on a lighter body is what pushes the bonus past 25 percent.
The calculator runs the original 1977 Pandolf form, exactly as RuckTrack does on the watch:
M is metabolic rate in watts, W body weight in kg, L pack weight in kg, V speed in m/s, G grade in percent, and η the terrain coefficient. Calories per hour are M × 3600 / 4184. Two guardrails carry over from the watch implementation: speed is capped at 2.5 m/s (5.6 mph) because the equation was validated for walking, and on descents the result is floored at the standing cost (the Santee correction) so a downhill never reads as free.
The full write-up, including the terrain research, the descent correction, and how RuckTrack blends in heart rate when GPS drops, is on the calorie math page.
RuckTrack runs this equation live during your ruck: speed from GPS, grade from a rolling barometric buffer, terrain from a picker, and an unloaded baseline computed in parallel so the pack bonus shows on the watch and lands in Garmin Connect. Treadmill rucks and vest walks are covered by two indoor modes. It is $2.99 on the Connect IQ store, with no account and no subscription.