§ 01 / TOOL
Male · 30 · 5'10" · 170lb.
STATUS ACTIVEFORMULA MIFFLINLATENCY <1MS
> INPUT
SEX
AGE
yrs
HEIGHT (FT / IN)
ft
in
WEIGHT (LB)
ACTIVITY LEVEL
MAINTENANCE CALORIES.
PER DAY
// TDEE
2,693 kcal
// BMR (AT REST)
1,737 kcal
// LOSE 1 LB/WK
2,193 kcal
// GAIN SLOWLY
2,993 kcal
// FORMULA
Mifflin-St Jeor · Moderate (×1.55)
At 30, male, 170 lb · 70 in, moderate (×1.55): your TDEE is 2,693 kcal/day. Eat that to maintain, 2,193 to lose ~1 lb/week, 2,993 to gain slowly.
§ 02 / ABOUT
How to use this.
TDEE — Total Daily Energy Expenditure — is the single most useful number in nutrition. It’s the calorie target every other plan either assumes or depends on. Eat that many calories and your weight stays the same. Eat less and you lose weight. Eat more and you gain. Everything else — intermittent fasting, specific macros, meal timing — is downstream of this one figure.
The calculator above uses the Mifflin-St Jeor equation, the current clinical standard. It takes your sex, age, height, and weight to compute BMR (basal metabolic rate — what you burn at complete rest), then multiplies by an activity factor to account for movement and formal exercise.
// HOW TO USE THE OUTPUT
- TDEE — eat this to maintain your current weight.
- LOSE 1 LB/WK — TDEE minus 500 calories, the standard sustainable fat-loss deficit.
- GAIN SLOWLY — TDEE plus 300 calories, a lean-gain surplus that minimizes fat gain.
// COMMON MISTAKES
- Picking an activity level too high. "Moderate" means 3–5 quality workouts per week. A desk job plus a daily dog walk is "light" at best. When in doubt, pick one level down — you can adjust up after a week of real data.
- Treating the output as gospel. Mifflin-St Jeor is accurate within ±10% for most adults. Your actual TDEE depends on muscle mass, thyroid function, and NEAT (non-exercise activity). Recalibrate every 2–3 weeks based on what the scale actually does.
- Not recalculating as you lose weight. A smaller body takes fewer calories to maintain. Every 10–15 pounds lost, your TDEE drops by 100–200 calories. This is why diets plateau. Recalculate monthly.
For the full walkthrough of how the formula works and why personal calorie math beats BMI classifications, read What is TDEE and why it matters more than BMI.
§ 03 / FAQ
Questions. Answered.
What is TDEE?+
Total Daily Energy Expenditure — the calories your body burns in a typical 24 hours. It includes your basal metabolic rate (what you burn at rest), the thermic effect of food, non-exercise movement (NEAT), and planned exercise. Eat exactly your TDEE and your weight stays the same; eat less or more to lose or gain.
How accurate is this calculator?+
Within about ±10% for most adults. The Mifflin-St Jeor formula is the current clinical standard but it can’t see your muscle mass, thyroid function, or individual metabolic quirks. Use the number as a starting point, then adjust every 2–3 weeks based on what your weight actually does.
Mifflin-St Jeor vs Harris-Benedict — which is better?+
Mifflin-St Jeor (used here). The 1990 revision was validated against modern populations and is more accurate on average — particularly for older adults and higher body weights. Harris-Benedict, published in 1919 and revised in 1984, tends to overestimate BMR for non-athletic adults.
How do I pick an activity level?+
Most people overestimate. "Sedentary" (×1.2) means desk job, no training. "Light" (×1.375) is a desk job plus 1–3 light workouts a week. "Moderate" (×1.55) is 3–5 solid workouts or an active job. "Very active" (×1.725) is hard training 6–7 days. "Extra active" (×1.9) is physical labor plus training. When in doubt, pick one step lower.
Why subtract 500 for weight loss?+
3,500 calories is roughly the energy in a pound of body fat. A 500-calorie daily deficit × 7 days ≈ 3,500 ≈ 1 pound/week. That’s the standard target: aggressive enough to see progress, mild enough to protect muscle and energy levels. Deeper cuts (1,000+/day) often backfire through muscle loss and rebound.
Does TDEE change as I lose weight?+
Yes. Every 10–15 lbs lost, your TDEE drops because a smaller body takes fewer calories to maintain. This is why plateaus happen. Recalculate every 4–6 weeks and adjust your intake down. A 2,400-calorie starting point might be 2,150 three months in — same deficit, smaller number.
Can I use this if I’m very muscular?+
Mifflin-St Jeor uses total body weight, so it underestimates for very lean, muscular people and overestimates for people with higher body fat. If you know your body fat percentage, the Katch-McArdle formula (uses lean body mass) is more accurate — we may add it as an option later.
§ 04 / TOOLS
Related calculators.
§ 05 / READING