AkCalculators

How many calories did I burn? Understanding METs, exercise intensity and practical calorie estimates

Estimating calories burned during exercise is a common question for people managing weight, monitoring training load, or planning nutrition. While direct measurement (indirect calorimetry in a lab) is the gold standard, most practical tools use Metabolic Equivalent of Task (MET) values to estimate energy expenditure. This article explains what METs are, how the standard formula works, why body weight and intensity matter, and how to use MET-based estimates sensibly in everyday life.

What is a MET?

A MET — metabolic equivalent — is a unit that describes the intensity of an activity as a multiple of resting metabolic rate. 1 MET is approximately the energy cost of sitting quietly and is typically defined as about 3.5 ml O₂ per kg bodyweight per minute. Activities are assigned MET values: for example, walking at 3.0–3.5 mph may be ~3–4 METs, while vigorous running exceeds 10 METs. MET tables are derived from population studies and standardized compendia of physical activities.

The MET-based calorie formula

This calculator uses the classic formula:

Calories (kcal) = MET × 3.5 × weight(kg) ÷ 200 × duration(min)

Why those numbers? MET × 3.5 × weight yields an estimate of oxygen consumption in ml/min; converting ml O₂ to litres and applying ~5 kcal per L O₂ leads to the ÷200 factor that collapses constants into one tidy step. The result gives kcal per minute, multiplied by duration (minutes) yields total kcal burned.

Why weight matters

Energy cost scales roughly with mass — moving a heavier body requires more energy for the same activity. That’s why calories burned for the same activity and duration will be higher for a 90 kg person than for a 60 kg person, even if both move at the same speed.

Intensity and MET variability

MET values are averages. Individual effort changes energy cost: a brisk walk can be easy for one person and demanding for another. That’s why the calculator includes an intensity modifier (low/moderate/high). For activities with wide intensity ranges (e.g., cycling, rowing, strength training) either choose the more specific activity entry or use the 'Custom MET' override if you have a measured MET value or a more suitable estimate.

Examples and interpretation

As an example, a 70 kg person jogging at 6 mph (≈9.8 MET), for 30 minutes:

Calories ≈ 9.8 × 3.5 × 70 ÷ 200 × 30 ≈ 360 kcal

That gives a practical number for planning energy intake around workouts. Remember MET estimates omit post-exercise oxygen consumption (EPOC) which can add a modest extra (~5–10% or more in very intense efforts) but varies.

Limitations of MET estimates

MET-based estimates are useful but approximate. They don't account for:

• Individual metabolic differences (e.g., higher basal metabolic rate, efficiency)
• Fitness level and movement economy (trained runners often use less energy at the same speed)
• Environmental factors (temperature, terrain, wind)
• Equipment and technique (e.g., cycling in high gear vs low gear)

Use the MET estimate as a practical guide, but if you need precise energy expenditure for athletic planning or clinical nutrition, consider metabolic testing or validated wearable devices with caution about their own limitations.

Using this estimate for weight and nutrition planning

When using exercise calorie estimates to plan eating, be cautious: overestimating calories burned leads to overeating if matched by food intake. A conservative approach is to assume the lower end of an estimate and monitor weight trends, performance and recovery. Combine exercise estimates with measured changes (scale trends over weeks) to calibrate your personal energy-balance models.

Practical tips

• If you know your heart-rate-based energy cost from a wearable or lab, prefer that over pure METs.
• Log typical activities and durations for several weeks to get realistic weekly energy expenditure.
• Factor in recovery calories (EPOC) only for high-intensity or prolonged sessions if you understand the likely additional cost.
• Use the custom MET override when you have a measured or more accurate MET for specialized exercise.

Disclaimer: Estimates are informational only and not a substitute for clinical or laboratory measurement. For clinical nutrition or precise athletic fueling, consult a dietitian or exercise physiologist.