Many people build calorie / macro tracker like OP but they don't build maintenance calorie tracker.

Your app tracks calorie intake, doesn't keep track of total calorie burn of the day (maintenance calorie tracking)

And no, calorie burn from watch is not good enough!

>A 2020 systematic review by Fuller et al. found that consumer wearables often perform poorly at estimating energy expenditure, even when they measure steps and heart rate reasonably well. Across brands like Apple, Garmin, Polar, and Withings, calorie burn estimates frequently showed substantial error, often in the 15–40% range and sometimes exceeding 50%. Wearables can still be useful for tracking trends, but not for precise calorie calculations.

Here's completely free one i built, https://macrocodex.app/ 16,000+ users already.