Rucking is the simple act of walking with a weighted pack on your back. Unlike standard walking, rucking significantly increases your metabolic rate due to the added load. This calculator utilizes the Pandolf Equation, which is the scientific gold standard used by military organizations to estimate the energy expenditure of soldiers carrying heavy loads.
The Pandolf Equation Logic
The calculation isn't just a simple multiplier. It takes into account several critical variables:
Body Weight (W): Your baseline mass that requires energy to move.
Load (L): The specific weight of your ruck or weighted vest.
Speed (V): Faster movement increases energy consumption exponentially.
Terrain (η): Walking on sand requires significantly more energy than walking on pavement.
Grade (G): The steepness of the incline increases the work performed against gravity.
Example Rucking Calculation
Consider a 200 lb individual carrying a 40 lb pack at a pace of 3.5 mph on a standard paved road with a 1% incline for 60 minutes:
Body Mass: 200 lbs (~90.7 kg)
Load: 40 lbs (~18.1 kg)
Speed: 3.5 mph (~1.56 m/s)
Formula Result: This individual would burn approximately 620 to 650 calories per hour, compared to roughly 350-400 calories for a standard walk without the pack.
Benefits of Rucking
Why choose rucking over standard cardio? Rucking is often called "active resistance training." It builds muscular endurance in the legs, back, and core while providing a cardiovascular workout that is less taxing on the joints than running. It is an ideal way to improve "functional fitness"—the type of strength and stamina required for real-world activities like hiking, moving heavy objects, or military service.
function calculateRuckCalories() {
// Get Inputs
var bodyWeightLbs = parseFloat(document.getElementById('bodyWeight').value);
var packWeightLbs = parseFloat(document.getElementById('packWeight').value);
var speedMph = parseFloat(document.getElementById('ruckSpeed').value);
var durationMin = parseFloat(document.getElementById('ruckDuration').value);
var gradePct = parseFloat(document.getElementById('ruckIncline').value);
var terrainFactor = parseFloat(document.getElementById('terrainFactor').value);
// Validation
if (isNaN(bodyWeightLbs) || isNaN(packWeightLbs) || isNaN(speedMph) || isNaN(durationMin)) {
alert("Please fill in all fields with valid numbers.");
return;
}
// Conversions
// lbs to kg
var W = bodyWeightLbs * 0.453592;
var L = packWeightLbs * 0.453592;
// mph to m/s (1 mph = 0.44704 m/s)
var V = speedMph * 0.44704;
// Grade as percentage (e.g. 5% = 5)
var G = gradePct;
// Terrain factor (eta)
var eta = terrainFactor;
// Pandolf Equation: Metabolic Rate (M) in Watts
// M = 1.5W + 2.0(W + L)(L/W)^2 + eta(W + L)(1.5V^2 + 0.35VG)
var loadRatio = L / W;
var part1 = 1.5 * W;
var part2 = 2.0 * (W + L) * (loadRatio * loadRatio);
var part3 = eta * (W + L) * (1.5 * (V * V) + 0.35 * V * G);
var watts = part1 + part2 + part3;
// Convert Watts to kcal/min
// 1 Watt = 0.01433 kcal/min (approximate metabolic conversion)
var kcalPerMin = watts * 0.01433;
// Total Calories
var totalKcal = kcalPerMin * durationMin;
var kcalPerHour = kcalPerMin * 60;
// Display results
document.getElementById('ruckResultBox').style.display = 'block';
document.getElementById('totalCalories').innerText = Math.round(totalKcal) + " kcal";
document.getElementById('calorieDetailText').innerText = "Estimated rate: " + Math.round(kcalPerHour) + " kcal per hour";
// Scroll to results on mobile
if (window.innerWidth < 600) {
document.getElementById('ruckResultBox').scrollIntoView({ behavior: 'smooth' });
}
}