How we count your calories
Most fitness apps count a ruck like a walk. Rucksteady counts the pack.
The model counts your pack, your speed and the slope
We use the Pandolf equation (1977). It estimates the energy cost of walking from four things: your body weight, the weight you carry, your speed and the slope. We add a small factor for mixed trails (1.1× a paved road). Your body and pack weight come from your profile and from the ruck itself.
For an 80 kg person walking at 1.5 m/s on the flat, the equation predicts about 484 W with a 16 kg pack instead of 417 W without one.
Three things we leave out on purpose
| Case | Counted as | Why |
|---|---|---|
| Downhill | Flat ground | The equation is not valid downhill |
| Faster than 6:40 min/km | That pace | Usually a GPS jump or a ride |
| Resting energy (Apple Health, Health Connect) | Subtracted | So your phone does not count it twice |
The number is an estimate, not a measurement
The model was built on soldiers, and newer US Army research shows that the classic equations underestimate the cost of heavy loads. Phone GPS adds its own error, especially on climbs.
Calories are a model estimate, not a measurement, and not medical or dietary advice.