Calories

How calorie estimates work

FitSum estimates the calories burned during each workout. These are estimates — not clinical measurements — but the app is designed to produce meaningful numbers that improve as it learns more about you.

The estimate combines several signals depending on what data is available. The more data you provide, the more accurate the estimate.

What feeds into the estimate

The exercise itself — Different exercise types burn calories at different rates. The app uses established physical activity data as a baseline, adjusted for your body weight.

Your body weight and age — Heavier individuals and younger individuals burn more calories performing the same work. Keep your body weight current (log it on the Progress → Body tab) for the most accurate estimates.

Your age group — The baseline metabolic rate used in the calculation is adjusted for age. Older adults have a slightly lower resting metabolic rate, which affects the estimate.

Heart rate data — If HR data is available (from a live Bluetooth monitor or a post-workout health sync), the app blends it into the estimate. HR is a direct signal of cardiovascular demand and produces a more accurate calorie figure than using exercise type and body weight alone.

RPE — If no HR data is available, RPE (your perceived effort rating) acts as a fallback intensity signal.

Equipment power — Some equipment (bikes with power meters, rowing machines) can report direct power output, measured in watts. FitSum uses this when you log it per set with the exercise; it's a stronger intensity signal than the usual estimated MET value.

Resting periods — Strength MET values are session averages that already account for the rest between sets, so the session isn't treated as continuous all-out effort.

Improving your calorie accuracy

These steps produce measurably better estimates, roughly in order of impact:

1. Wear a heart rate monitor — Live HR data is the biggest accuracy improvement available.
2. Log RPE for every exercise — Even without HR, a consistent effort rating helps the engine calibrate intensity.
3. Connect Apple Health or Health Connect — Post-workout HR enrichment from your health platform improves estimates even without a Bluetooth monitor.
4. Keep your body weight current — Log weight regularly in the Body tab. An outdated weight leads to systematically off estimates.
5. Keep your profile age current — Set your date of birth in your profile, not just your current age.

Why my calorie estimate seems low or high

Too low

• Body weight in your profile may be significantly out of date
• RPE ratings were skipped or consistently under-estimated
• No HR data was available for a high-intensity session

Too high

• A long session time combined with missing rest data can inflate estimates
• Body weight logged may have been recorded when heavier

If estimates are consistently off, check your profile data first. Then check that health integration is connected and HR is being pulled in after sessions.

Calories on the widget and Progress tab

The calorie figure on the widget and the Progress → Activity tab reflects estimated active calories for the day. This includes:

• Calories from FitSum workouts completed today
• Active calories imported from Apple Health / Health Connect (if enabled)

Resting metabolic calories (what you burn just by existing) are not included. The figures shown are active / exercise calories only.

Calories are not used to gate food

FitSum does not recommend food intake, calorie targets, or eating behaviour. The calorie figures are informational only. If you're using calorie data to manage intake, please consult a registered dietitian.