How to measure your maintenance calories
17 August 2026
Every calorie calculator asks the same four things: height, weight, age, sex. Then it multiplies by an “activity level” you picked from a dropdown. Out comes a confident number like 2,340.
That number is an average of people who share your measurements. You are not the average of those people. Real metabolic rates vary meaningfully between individuals of identical size, and the activity multiplier — the part you guessed at — swings the answer by hundreds of calories on its own.
The measurement that beats the estimate
You do not have to guess, because you are running an experiment on yourself every single day. Energy balance says:
burn = intake − (weight change × 7700 ÷ days)
7,700 calories is roughly one kilogram of body fat.
Worked through: suppose over 14 days you averaged 2,000 calories a day, and your trend weight fell 0.8 kg. That 0.8 kg represents about 6,160 calories, or 440 a day. So your actual burn is about 2,440 — not the 2,100 the calculator told you.
Notice what this figure already includes: your workouts, your fidgeting, your job, your terrible sleep, your particular thyroid. You did not have to estimate any of it, because it all showed up in the weight change.
Doing it properly
The method is simple; the ways to get it wrong are the interesting part.
- Use trend weight, not raw weigh-ins. Both ends of your window are single mornings, and single mornings carry a kilo of water noise. That noise maps onto roughly 550 calories a day of error over a fortnight — enough to make the answer worthless. Smooth first. (Why the scale lies most days.)
- Use at least two weeks. Shorter windows are dominated by whatever your water is doing.
- Log honestly, including the bad days. This is the one that quietly ruins the calculation. If you under-record, the maths concludes you burn less than you do, and it hands you a lower target — which makes the next fortnight harder for no reason.
- Do not count a day you forgot to log as zero calories. A missing day is missing data. Treating it as a fast will drag your average down and inflate your apparent burn rate.
- Recalculate as you go. Your burn falls as you get lighter — a smaller body costs less to run. A figure measured 15 kg ago is out of date.
Why not just use your watch?
Because you would be importing its error. Wrist-based active-energy figures are estimates built from heart rate and movement, and they are known to be unreliable for calorie burn specifically, even when their heart-rate tracking is good. More to the point, they are unnecessary here: the weight-change method already contains every calorie you burned, whether or not any device noticed you burning it. Adding the watch’s number on top double-counts and imports a guess into a measurement.
Movement data is still useful — as context for why a particular day was unusual. It just should not be the source of your target.
What Cut does with it
Cut runs this calculation continuously on a rolling window of your own data, and sets your daily target from the result. The deficit is sized as a percentage of your bodyweight, so it eases off as you get closer to your goal rather than staying brutally fixed. There is a hard floor the target will never go below, whatever the arithmetic suggests.
Until it has enough of your data to measure honestly — about a fortnight of logging, with weigh-ins spread across it — it uses the standard formula and labels it as a fallback. An estimate presented as a measurement is the thing this whole approach exists to avoid.