§ · TDEE
TDEE calculator.Mifflin or Katch.
Same math BiteDeck runs on your phone, in a one-shot web form. Pick the formula, plug in your numbers, read the result.
§ · Calculator
Mifflin–St Jeor or Katch–McArdle§ 01 · How TDEE works
BMR is the energy your body burns at rest — breathing, circulation, organ function. TDEE is BMR multiplied by an activity factor that accounts for everything else: walking, training, fidgeting, thinking.
Your daily intake against TDEE is your deficit (loss) or surplus (gain). One pound of fat is roughly 3,500 kcal — but that's a rule of thumb, not a contract. Real-world results lag the math by a week or two, and water shifts can mask actual change for several days at a time.
§ 02 · Mifflin–St Jeor vs. Katch–McArdle
Two formulas, two philosophies. Mifflin–St Jeor reads total body weight; Katch–McArdle reads lean mass. Here is each one, written out.
The Mifflin–St Jeor formula
Men: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age + 5
Women: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age − 161
Uses sex, age, height, and weight. Reasonable for most people. Tends to over-estimate at high body fat and under-estimate for very lean athletes.
The Katch–McArdle formula
BMR = 370 + 21.6 × lean body mass(kg), where lean body mass = weight × (1 − body fat % / 100).
Uses lean body mass instead of total weight, so it is more accurate at the tails of body composition. The catch: you need a body-fat number you trust. If you don't, the US Navy body-fat calculator gets you a usable estimate in two minutes.
§ 03 · Activity factor, demystified
The activity factor is the softest part of the calculation. Multiply your BMR by the multiplier that matches your week. The five-level breakdown is conventional but coarse:
Sedentary — ×1.2
Desk job, little or no exercise.
Lightly active — ×1.375
Light exercise 1–3 days a week.
Moderately active — ×1.55
Moderate exercise 3–5 days a week.
Very active — ×1.725
Hard exercise 6–7 days a week.
Extra active — ×1.9
A physical job plus daily training.
If you're between two levels, pick the lower one for two weeks and adjust based on actual weight change. The number is an estimate either way.
§ 04 · How BiteDeck uses this
In the app, this calculation runs daily — against your logged weight, your saved body fat %, and your activity (HealthKit imports help here). The forecast watches the rolling average against the projection and tells you when the trend reverses. See On-device weight forecasting for the rest of the math.
§ 05 · FAQ
How accurate is a TDEE calculator?
Treat the number as a starting estimate, not a measurement. The formulas are population averages, and your real expenditure varies with NEAT, sleep, and day-to-day activity. Log your intake against it for two weeks, watch the trend in your weight, and adjust — that calibration is what makes it accurate for you.
How many calories should I eat to lose weight?
Subtract a deficit from your TDEE. A daily 300–500 kcal deficit is a sustainable rate for most people — roughly 0.5–1 lb per week. Bigger deficits lose faster but are harder to hold and cost more lean mass. Re-check against actual weight change every couple of weeks.
Should I use Mifflin–St Jeor or Katch–McArdle?
Use Mifflin–St Jeor if you do not have a reliable body-fat number — it only needs sex, age, height, and weight. Use Katch–McArdle if you do have a measured body-fat %, because it works from lean mass and is more accurate at the lean and high-body-fat extremes.
Does TDEE include exercise?
Yes. TDEE is BMR multiplied by an activity factor, and that multiplier is meant to cover your training and daily movement. Do not also subtract exercise calories on top — that double-counts the burn and leaves you under-eating.
How often should I recalculate my TDEE?
Whenever your weight moves about 10 lb, or your activity level changes meaningfully. TDEE scales with body mass, so as you lose or gain, the number drifts. BiteDeck handles this for you — it reruns the math daily against your logged weight on the device.