I built PackCal, a single Garmin data field that counts the calories your weighted vest or pack adds. It is for anyone who carries weight on foot, from daily vest walkers to ruckers, loaded hikers, hunters, snowshoers, and mountaineers. What sets it apart from a generic Walk or Hike profile is the calorie math: it accounts for the load you carry, not just your heart rate. After you save, it writes pack weight, load-aware calories, and terrain factor to Garmin Connect, under Stats in the Connect IQ section.
The calorie math
The native estimate reads your effort mostly through heart rate, so it captures only part of what a pack adds. The heavier the load, the bigger the gap. PackCal runs the Pandolf load-carriage equation, the model U.S. Army research validated for marching under load, so your body weight, pack weight, speed, terrain, and grade all move the number.
Because it is a data field and not a separate app, you add it inside an activity you already use and it adds one number without taking anything away. You keep Garmin's turn-by-turn navigation, loaded courses, maps, and every native field. PackCal fills in the load-aware calorie number Garmin leaves out.
It keeps counting indoors or out, GPS or not. On a treadmill or indoor walk, it scales the watch's own estimate by your load. Outdoors, during warm-up, under heavy tree cover, or on a stop partway up a hill, it falls back to that estimate and resumes the full load-aware math once the signal returns.
One cell, adaptive
Give PackCal a full single-field screen and it shows your key activity numbers at once: the calorie total big and center, live heart rate, pace, and ascent down one side, time and distance along the bottom, and a CAL FROM PACK panel showing what the load adds. A line echoes your setup, like "15 lb · Trail", so you can confirm it at a glance. In a denser multi-field layout the same field degrades cleanly to a labelled number.
A few details that matter for accuracy:
- Terrain coefficients from the model: Road 1.00, Gravel 1.05, Trail 1.20, Sand 1.50, Snow 2.50.
- Speed capped at 2.5 m/s, since the equation is validated for walking pace.
- A 60-second rolling grade buffer with a 30 m minimum-distance guard, so brief altitude spikes don't pollute the burn rate.
- Body weight resolves from your override, then your Garmin profile, then asks you to set it. It never silently guesses a default.
Setting it up
Set everything right on the watch: in the activity, hold the menu button, pick Connect IQ Fields, then PackCal, and set pack weight, units, terrain, and energy unit (plus a body weight if your Garmin profile has none). Change your load mid-activity and it updates within a second. Or open PackCal in the Connect IQ app, where the same settings live.
Where it works, and where it won't
Walk, Hike, and Ruck run the full model, and so do Hunting, Snowshoeing, Mountaineering, and similar load-carrying activities. A child carrier counts too, as the same Hike with the carrier and kid as your load.
Everywhere else it shows two dashes on purpose. The Pandolf model is validated for walking, not running, and on a bike, in the water, or in the gym your load isn't what's costing you. Rather than show a number it can't stand behind, PackCal refuses to guess.
For a sense of scale: a 10 lb vest adds roughly 4 to 7 percent over the same walk unloaded, a 35 lb ruck 15 to 25 percent, and a 60 lb load 30 to 45 percent, depending on your body weight and grade.
Price and the full app
PackCal is $1.99 through Garmin Pay, with no unlock codes, account, subscription, ads, or tracking. It runs entirely on your watch, collecting nothing about you.
If you want a full app rather than a single cell, RuckTrack from the same developer is the other shape: a complete app for ruck, hike, weighted vest, and treadmill, with multiple live screens, load presets, and a post-activity summary. Both use the same calorie math, so your numbers agree across them.
PackCal runs on Garmin watches with Connect IQ 5.0 and newer, including the Forerunner 70, 165, 170, 255, 265, 570, 955, 965, and 970, the fēnix 7 and 8 families and fēnix E, epix and epix Pro, Enduro 3, Venu 2, 3, 4, X1, and Sq 2, Instinct 3 and Instinct Crossover (AMOLED), and vívoactive 5 and 6.
Store: PackCal on the Connect IQ Store.
How the calorie math works, FAQ, and support: the PackCal docs.
Happy to hear from anyone running it, especially weighted-vest walkers. Feedback, bug reports, and feature requests all welcome.