Calorie calculator

Enter your distance, time and the gradient you covered. Most calculators ignore incline entirely, which is why they under-report hilly routes badly — walking up a 10% gradient costs 2.3x what the same walk costs on the flat.

How this is calculated

Most online calorie calculators multiply a single MET value by your weight and time. That is fine on flat ground and wrong everywhere else, because it has no way to account for gradient.

This one uses two different models depending on what you are doing.

Walking and running

The ACSM metabolic equations, which are standard in exercise physiology and take grade as an explicit input:

Walking: VO₂ = (0.1 × speed) + (1.8 × speed × grade) + 3.5 Running: VO₂ = (0.2 × speed) + (0.9 × speed × grade) + 3.5

Speed is in metres per minute, grade is a fraction, and VO₂ comes out in ml/kg/min. Oxygen consumption converts to energy at roughly 5 kcal per litre.

Note the grade coefficient: 1.8 for walking against 0.9 for running. Climbing penalises walkers twice as much per unit of grade, which is why a steep hill turns a walk into a genuinely hard effort while runners lose comparatively less.

Cycling

Cycling is not well served by MET tables, because air resistance dominates and scales with the cube of speed in power terms. So this uses a physical model of the forces you are actually overcoming:

Power = (rolling resistance + gravity + aerodynamic drag) × speed

with rolling resistance at 0.006, drag area CdA at 0.40 m² (a normal position on the hoods, not a racing tuck), air density 1.225 kg/m³, and a 10 kg bike. Mechanical power is divided by 0.24 — human muscular efficiency — to get metabolic cost.

That efficiency figure is the reason cycling burns so much: roughly three quarters of the energy you produce leaves as heat rather than propulsion.

Gross versus net calories

The large number is gross — total energy expended.

The smaller figure is net, with your resting metabolism subtracted. You would have burned those calories lying on the sofa, so if you are counting calories against food intake, net is the honest number.

For an hour of exercise the difference is typically 60–100 kcal. Most fitness apps report gross, which is one reason app estimates tend to look generous.

How accurate is any of this?

Roughly ±10–20% for an individual, at best. Treat the output as a good estimate, not a measurement.

Sources of error that no calculator can see:

• Efficiency varies between people by 5–10%, and trained athletes are more economical than beginners at the same speed.
• Terrain and surface. Sand, mud, snow and rough trail cost far more than the equivalent distance on tarmac.
• Wind. For cycling this is enormous — a headwind can double your power output at the same ground speed, and the calculator has no way to know.
• Body composition. Muscle and fat have different metabolic costs to carry.
• Temperature. Both heat and cold add metabolic load.

The relative numbers are more trustworthy than the absolute ones. If it says today's hilly walk cost 40% more than yesterday's flat one, believe that — even if both absolute figures are 15% off.

Rough reference figures

For a 70 kg person on level ground:

The pattern worth noticing: running costs roughly the same per kilometre regardless of speed, because you are lifting your body weight the same number of times either way. Cycling is the opposite — cost per kilometre rises steeply with speed, since drag grows with the square of velocity.

Walking is the most efficient per kilometre. It simply takes longer.

Measuring the inputs

The calculator is only as good as the distance and time you feed it. Self Speed records both automatically, along with your average speed — see average walking speed and average cycling speed for what to expect.

Incline is the one figure GPS handles poorly. Vertical accuracy is typically two to three times worse than horizontal, so for a route with meaningful climbing, take the gradient from a mapping tool rather than from your phone.