User Guide
Step 1 — Enter your details
- Add your measurements and pick your options.
Step 2 — Read the dashboard
- Results, gauge and breakdown update instantly.
Step 3 — Explore the detail
- Review the per-method figures and personalised guidance.
Step 4 — Export
- Download a PDF report or print it.
About the Calorie Calculator
This tool works out how many calories you need each day — to maintain, lose or gain weight — and turns that into an actionable plan: macro targets, a sensible meal split, an estimated rate of change, and a timeline to a goal weight, with a downloadable report.
From BMR to your daily target
It estimates your Basal Metabolic Rate with the Mifflin–St Jeor equation — widely regarded as the most accurate of the common formulas — then multiplies by an activity factor to give your maintenance calories (TDEE). Your chosen goal applies a moderate adjustment on top: a deficit for fat loss or a small surplus for gain. The activity multiplier is where people most often go wrong by overestimating; when unsure, choose the lower option and refine from real-world results.
Macros, meals and a safe pace
Calories decide weight; macros and food quality shape body composition and how you feel. The tool sets a protein target near 1.8 g/kg to preserve muscle, allocates around a quarter of calories to fat, and fills the rest with carbohydrate — then splits the day into breakfast, lunch, dinner and a snack so the numbers are usable. Crucially, it keeps you safe: it will not target unsafe ultra-low intakes, capping at a sensible floor and steering you toward adding activity instead of starving. Sustainable change of around half a kilo per week beats crash dieting, which sheds muscle and rarely lasts.
The formula, written out
Your Basal Metabolic Rate comes from the Mifflin–St Jeor equation, published in 1990 and still the best-validated predictive equation for healthy adults:
Men: BMR = (10 × weight kg) + (6.25 × height cm) − (5 × age) + 5
Women: BMR = (10 × weight kg) + (6.25 × height cm) − (5 × age) − 161
BMR is what your body burns at complete rest. To get maintenance calories (TDEE) it is multiplied by an activity factor:
| Activity level | Typical week | Factor |
|---|---|---|
| Sedentary | Desk job, little deliberate exercise | 1.2 |
| Lightly active | Light exercise 1–3 days | 1.375 |
| Moderately active | Moderate exercise 3–5 days | 1.55 |
| Very active | Hard exercise 6–7 days | 1.725 |
| Extra active | Physical job or twice-daily training | 1.9 |
Worked example
A 30-year-old woman, 65 kg, 165 cm, moderately active:
BMR = (10 × 65) + (6.25 × 165) − (5 × 30) − 161 = 650 + 1,031 − 150 − 161 = 1,370 kcal
TDEE = 1,370 × 1.55 = 2,124 kcal to maintain her weight.
For fat loss, a 500 kcal daily deficit puts her at about 1,624 kcal — roughly 0.45 kg (1 lb) a week, since a kilogram of body fat represents roughly 7,700 kcal. A 35-year-old man, 80 kg, 178 cm, lightly active works out at BMR 1,743 kcal and TDEE 2,396 kcal, which shows how much of the difference between two people is simply body size and sex rather than metabolism being “fast” or “slow”.
Treat it as a starting point
Every equation is an approximation, and your true needs depend on genetics, NEAT and body composition. Use these figures as a baseline, watch your weight trend over two to three weeks, and nudge intake up or down. This tool gives general information for education, not medical or dietetic advice; consult a qualified professional for guidance about your health. For the underlying metabolic numbers see the BMR & TDEE Calculator.
Sources & further reading
- Mifflin MD, St Jeor ST, et al. “A new predictive equation for resting energy expenditure in healthy individuals.” American Journal of Clinical Nutrition, 1990 — the equation used here.
- National Heart, Lung, and Blood Institute (NIH) — weight, BMI and energy-balance guidance.
- World Health Organization — Obesity and overweight fact sheet — population definitions and health context.
Frequently Asked Questions
How are my calories calculated?
Your BMR is estimated with the Mifflin–St Jeor equation, then multiplied by an activity factor to give maintenance calories (TDEE). Your goal then adds or subtracts a moderate amount.
How are the macros decided?
Protein is set near 1.8 g per kg of body weight to protect muscle, fat at about 25% of calories, and carbohydrate fills the remainder. It is a flexible starting split you can adjust to your preferences.
Why won’t it let me go very low?
Very low-calorie diets risk muscle loss, nutrient gaps and rebound, and are not safe without medical supervision. The tool floors intake at a sensible minimum and suggests adding activity rather than cutting food further.
How fast can I expect to lose weight?
A deficit of about 500 kcal/day tends to produce roughly half a kilo per week, which is sustainable. The tool shows your estimated rate and a timeline if you enter a target weight.
Are these numbers exact?
No — they are estimates from prediction equations and vary with genetics and body composition. Track your real results for 2–3 weeks and adjust intake by 100–200 kcal as needed. This tool gives general information for education, not medical or dietetic advice; consult a qualified professional for guidance about your health.
