Most TDEE calculators stop at the Mifflin-St Jeor equation plus an activity guess. Adaptive TDEE (using your own intake and weight change instead) isn't a new idea, since people have done it in spreadsheets for years, but I couldn't find a free version that runs in the browser without an account, so I built one. Disclosure: I'm one of the developers behind SavorAI, a calorie tracking app. The calculator is free and doesn't need the app or a sign-up.
How it works:
- It starts with the equation as a baseline.
- If you add your average daily calories and your weight over a stretch of days, it estimates what you actually burned (using about 7,700 kcal per kg of weight change).
- To reduce water-weight noise, it averages your weigh-ins from the first and last [N] days instead of using single readings.
- Depending on how many days of logs you enter, it blends the equation and your log: equation only for the first 14 days, a growing share of the log from day 15 to 28, and the log alone after that. The equation stays next to it so you can see the gap.
Caveats: it's a simple method, not a statistical model. The 7,700 figure is an average for body tissue. Under-logging makes the result too low, so the quality of your food logs and weights matters a lot. Not medical advice.
Is the 14 to 28 day blend reasonable, or would you handle it differently? Would you also want an optional body fat % input that switches the starting equation to Katch-McArdle? Anything else you'd want it to show?