Normal: your weight is in the healthy range — keep any deficit gentle.
what your body burns per day, activity included
A starting estimate, not medical advice.
your calorie needs come from the Mifflin-St Jeor equation — a basal metabolic rate based on height, weight, age, and sex, multiplied by an activity factor between 1.2 and 1.725.For weight loss, subtract 10–20% from the result: that's roughly 0.5–1 lb per week without putting your body under stress.
The calculator above does three jobs at once: it estimates your body mass index, your maintenance calories, and a sensible calorie target for losing weight. Here's a quick tour of where those numbers come from and what to do with them.
01. How the calorie calculator works
First, the calculator estimates your basal metabolic rate (BMR) — the energy your body burns just staying alive: breathing, heartbeat, brain, and organs. We use the Mifflin-St Jeor equation, which the Academy of Nutrition and Dietetics considers the most accurate formula outside a lab: for men it's 10×weight + 6.25×height − 5×age + 5, for women the same with −161 at the end.
That number is then multiplied by an activity factor: 1.2 for a mostly sedentary life, 1.375 for light exercise 1–3 times a week, 1.55 for 3–5 workouts, and 1.725 for training almost daily. The result is your TDEE — maintenance calories, the daily intake that keeps your current weight steady.
02. What BMI actually tells you
Body mass index is your weight in kilograms divided by your height in meters squared. It's a quick check of how your weight relates to your height:
| BMI | Category |
|---|---|
| under 18.5 | below normal |
| 18.5–24.9 | normal |
| 25–29.9 | overweight |
| 30 and up | obese |
Know its limits, though: BMI can't tell muscle from fat, so muscular people often score "overweight" without carrying an extra pound of fat. Treat it as a directional signal, not a diagnosis — our article "BMI: what it shows and when it lies" digs into the details.
03. Which deficit to pick
The calculator offers three deficit options, and each has its use case:
- −10% — the gentlest: slower progress, but no hunger, no crashes, and minimal muscle loss. Best if you're close to your goal or new to dieting;
- −15% — the sweet spot: visible progress on the scale while keeping enough energy for training and everyday life;
- −20% — the upper limit of sensible: faster results, but higher demands on protein, sleep, and consistency. Going deeper usually backfires with fatigue and stalled progress.
pick a −10–15% deficit, lock in your target number, and live with it for 2–3 weeks, weighing yourself under the same conditions. If you're averaging 0.5–1 lb down per week, it's working — change nothing.
04. Why the number is a starting point, not a verdict
Every formula carries roughly ±10% error: two people with the same height and weight can burn noticeably different amounts thanks to body composition, hormones, and even how much they fidget. So treat the calculator's output as a first estimate.
The verification is simple: hold your target intake for two or three weeks and watch your weekly average weight. If the scale doesn't move on a "deficit," your real burn is lower than estimated — trim another 100–150 kcal. If weight drops too fast and your energy tanks, add some back. That loop of "estimate → observe → adjust" beats any formula.
05. Common questions
"Can I eat under 1,200 kcal to lose weight faster?" — not a good idea: it's hard to cover protein, vitamins, and minerals at that level, and rapid losses tend to rebound. "Do I need to recalculate?" — yes, after every 10 lbs lost and whenever your activity changes. "Why do different calculators give different numbers?" — formulas and multipliers vary; what matters isn't the perfect starting number but tracking how your body responds.
The bottom line
Enter your stats, get your maintenance number, and pick a gentle −10–15% deficit. From there, consistency beats precision: same intake daily, same weigh-in conditions, and a small adjustment every two or three weeks based on your weekly average. The calculator gives you the starting line — the system gets you to the finish.
This material is for informational purposes and does not replace medical advice.
