Estimates from general formulas, not medical advice. Check with a doctor before big changes to diet or training.
Swimming laps at a moderate pace is rated 6 MET in the Compendium of Physical Activities. Calories = MET × body weight in kg × hours, so 30 minutes burns about 180 kcal at 60 kg (132 lb), 210 kcal at 70 kg (154 lb) and 270 kcal at 90 kg (198 lb). Change the time and weight above for your own number.
How to use
- Pick a calculator in the tabs and choose metric or imperial units; the choice is remembered.
- Body fat: measure your neck below the larynx, your waist at the navel (men) or narrowest point (women) and hips at the widest point, then enter them. Or switch to From BMI.
- Ideal weight: enter height and sex. One-rep max: enter the weight and reps of a hard set. Calories: pick an activity and minutes. Water: weight and daily exercise. Steps: step count and your height or stride.
- Results update as you type. Tap any result to copy it.
- The US Navy method (Hodgdon and Beckett, 1984) is usually within 3–4 percentage points of a DEXA scan. The BMI method (Deurenberg, 1991) is rougher and overestimates fat in muscular people.
- Ideal weight formulas were made for drug dosing, not as health targets; the BMI range is a broader guide.
- 1RM: Epley = w × (1 + reps/30), Brzycki = w × 36 / (37 − reps), Lombardi = w × reps^0.10. All are most accurate for 2 to 10 reps.
- Calories use MET × weight (kg) × hours from the Compendium of Physical Activities and include your resting burn. Fitness trackers and machines may show different numbers.
- Water: about 35 ml per kg plus exercise. Food covers roughly 20% of water intake; EFSA suggests about 2.0 L a day for women and 2.5 L for men from all sources.
How it is calculated
Calories = MET × body weight in kg × hours. One MET is roughly the energy you use sitting quietly, about 1 kcal per kg per hour. Brisk walking at 3.5 MET for 30 minutes at 70 kg burns 3.5 × 70 × 0.5 ≈ 123 kcal; running at 9.8 MET for the same time burns about 343 kcal.
The result is gross energy and includes the calories you would have burned at rest anyway. For the extra calories from exercise alone, subtract about 1 MET.
Why trackers show different numbers
Watches and gym machines use heart rate, pace and their own models, and often read higher. Fitness level, terrain, wind, technique and temperature all change the real cost. Treat any figure as an estimate within about 20% and look at trends over time rather than single sessions.
These are estimates from general formulas, not medical advice. Nothing you enter leaves your device.
Frequently asked questions
How many calories do I burn walking 30 minutes?
At about 3 mph (4.8 km/h), a 70 kg (154 lb) person burns roughly 120 kcal; a heavier person burns more.
What is a MET?
A metabolic equivalent: the energy cost of an activity relative to sitting at rest. An activity of 6 MET uses about six times the energy of resting.
Does body weight change calories burned?
Yes. Moving a heavier body costs more energy, so the same activity burns proportionally more calories for heavier people.
Why does my fitness watch show more?
Devices use their own algorithms and often include assumptions about effort. Differences of 10–30% are common.
Which activities burn the most calories per hour?
Fast running, jumping rope and stair climbing are among the highest, around 9–12 MET, compared with 3–4 MET for walking.