Free TDEE & BMR Calorie Calculator — 3 Formulas, All Activity Levels & Macros
How many calories do you need per day? The answer depends on two numbers: your BMR (Basal Metabolic Rate — calories burned at rest) and your TDEE (Total Daily Energy Expenditure — calories burned including activity). This calculator computes both using the three most validated scientific formulas, shows you every activity level simultaneously, calculates your macros, and estimates your goal timeline — all in one place, with no signup required.
Unlike basic calorie counters that give you a single number and no explanation, this tool shows the math step by step and lets you compare Mifflin-St Jeor, Harris-Benedict, and Katch-McArdle side by side so you understand exactly where the number comes from and which formula best fits your body.
How to Use the Calorie Calculator
You get personalized results the moment you adjust the inputs — no submit button needed:
- Choose your units and biological sex — select Metric (kg/cm) or Imperial (lb/in), then Male or Female. Sex affects the BMR constant in every formula.
- Enter your age, weight, and height — these are the core inputs for Mifflin-St Jeor and Harris-Benedict. For most people, these three numbers are enough.
- Add your body fat percentage (optional) — entering a body fat percentage unlocks the Katch-McArdle formula, which is the most accurate option for muscular individuals or anyone who knows their body composition from a DEXA scan or calipers.
- Select your activity level — click any row in the activity table on the right to set your TDEE. The table shows all five levels simultaneously so you can see the full range.
- Review your results — BMR from all three formulas appears at the top. The TDEE table, step-by-step calculation, goal timeline, and macros update automatically.
Calorie Calculator Examples
30-year-old woman, 65 kg, 165 cm, moderately active (×1.55), 25% body fat:
| Formula | BMR | TDEE (moderate) |
|---|---|---|
| Mifflin-St Jeor | 1,370 kcal | 2,123 kcal |
| Harris-Benedict | 1,430 kcal | 2,217 kcal |
| Katch-McArdle (25% BF) | 1,423 kcal | 2,206 kcal |
28-year-old man, 75.5 kg, 180 cm, moderately active (×1.55):
| Formula | BMR | TDEE (moderate) |
|---|---|---|
| Mifflin-St Jeor | 1,784 kcal | 2,765 kcal |
| Harris-Benedict | 1,822 kcal | 2,824 kcal |
Edge case — very muscular person (85 kg, 180 cm, 12% body fat):
The Mifflin-St Jeor formula gives BMR = 1,859 kcal; Katch-McArdle gives BMR = 1,962 kcal. The 103 kcal difference is significant — Katch-McArdle is more accurate here because it uses lean body mass directly, not penalizing the extra muscle mass that Mifflin-St Jeor interprets as general weight.
BMR and TDEE — What They Are and Why They Matter
BMR (Basal Metabolic Rate) is the calories your body burns at complete rest — just to breathe, pump blood, regulate temperature, and keep organs functioning. It accounts for 60–75% of total daily energy expenditure for most people. BMR decreases with age (roughly 2–3% per decade after 30) and increases with muscle mass.
TDEE (Total Daily Energy Expenditure) is BMR multiplied by an activity factor that accounts for how much you move. It has four components: BMR (~65%), the thermic effect of food (~10%, with protein at 20–30%), exercise (~5–15%), and non-exercise activity thermogenesis or NEAT (~15–30%, covering all incidental movement).
The three formulas differ in what they use as inputs. Mifflin-St Jeor and Harris-Benedict both use weight, height, age, and sex — but were derived from different populations (Mifflin in 1990 vs. Harris-Benedict in 1919). Katch-McArdle bypasses the weight-as-proxy problem entirely by using lean body mass, making it the most accurate formula for people whose body composition deviates significantly from average.
Common Use Cases
- Weight loss planning: Calculate your TDEE, then subtract 500–550 kcal/day for approximately 0.5 kg/week of sustainable fat loss. The goal timeline shows exactly how many weeks to your target weight.
- Muscle gain (lean bulk): Add 275–550 kcal/day above TDEE. The macros section calculates your protein target (typically 1.6–2.2g/kg) to support muscle protein synthesis.
- Maintenance and tracking: Use TDEE as a baseline. If your actual weight changes differently than expected after 2–3 weeks, adjust the activity multiplier rather than the formula — the multiplier is the main source of real-world error.
- Comparing your body composition impact: Enter different body fat percentages to see how Katch-McArdle diverges from Mifflin-St Jeor — the gap reveals how much your body composition affects your metabolic rate.
- Understanding activity level impact: The TDEE table shows all five levels at once. The difference between sedentary (×1.2) and very active (×1.725) is 500–900 kcal/day depending on BMR — equivalent to running 8–15 km daily.
Common Mistakes with TDEE Calculators
- Overestimating activity level: The most frequent error. "Moderately active" (×1.55) means 3–5 days of genuine moderate exercise on top of an active daily life. A desk job with three 45-minute gym sessions is typically "lightly active" (×1.375). If your results seem too high, drop one activity level.
- Ignoring the activity multiplier problem: Even a perfect BMR formula contributes only ±5–10% error. Activity multipliers add another ±15–20%. The combined error range of TDEE calculators is typically ±10–15% — treat your result as a starting point, track for 2–3 weeks, and adjust by 100–200 kcal.
- Not recalculating when weight changes: Your TDEE decreases as you lose weight. For every 5–10 kg of weight loss, recalculate BMR and TDEE, or your calorie deficit will shrink invisibly and weight loss will stall.
- Using BMR for daily planning: BMR is your resting metabolic rate, not your daily calorie target. Always use TDEE (BMR × activity factor) as your baseline.
Frequently Asked Questions
How many calories do I need per day?
Your daily calorie needs equal your TDEE — Basal Metabolic Rate multiplied by your activity level. Most adults need between 1,600 and 3,200 kcal/day. A sedentary 30-year-old woman at 65 kg needs roughly 1,640 kcal to maintain weight; a very active 25-year-old man at 80 kg needs roughly 3,500 kcal. This calculator uses the Mifflin-St Jeor equation by default, which has been validated as the most accurate for modern adults in multiple clinical studies.
What is the difference between BMR and TDEE?
BMR is your resting metabolic rate — the calories your body burns doing nothing. TDEE is your total daily burn, which equals BMR × activity multiplier. If you eat at your TDEE, your weight stays constant. Eat below it to lose weight, above it to gain. Most people's TDEE is 1.3–1.9× their BMR depending on activity level.
Which BMR formula is most accurate — Mifflin-St Jeor or Harris-Benedict?
Studies consistently show Mifflin-St Jeor is the most accurate for most modern adults, predicting RMR within 10% in about 82% of cases versus 77% for Harris-Benedict. Harris-Benedict was developed in 1919 from a smaller sample and tends to overestimate BMR slightly. For people who know their body fat percentage from a DEXA scan, Katch-McArdle is typically the most accurate because it uses lean body mass directly.
What is a safe calorie deficit for weight loss?
A deficit of 500–550 kcal/day (producing approximately 0.5 kg/week loss) is the most commonly recommended safe range — it minimizes muscle loss, is nutritionally sustainable, and produces consistent results. Deficits of 750–1,100 kcal/day (0.75–1.0 kg/week) are acceptable short-term with high protein intake (≥1.6g/kg). Never go below 1,200 kcal/day for women or 1,500 kcal/day for men without medical supervision, as it becomes extremely difficult to meet micronutrient needs below these thresholds.
How accurate are calorie calculators?
TDEE calculators have an estimated error of ±10–15% because the activity multipliers are inherently imprecise and individual metabolic variation is significant. No formula can account for individual NEAT (non-exercise movement), metabolic adaptation, or medication effects. Treat your calculated TDEE as a starting estimate: track your weight and energy intake for 2–3 weeks, and if you're gaining or losing faster or slower than expected, adjust by 100–200 kcal. The formula is correct; the inputs are approximations.
Does this calculator support pounds and inches?
Yes — toggle "Imperial" at the top of the inputs. Weight is entered in pounds, height in inches. All calculations convert to metric internally (the formulas require kg and cm), then display results in kcal which are the same in any unit system.
Resources
- Mifflin MD et al. — "A new predictive equation for resting energy expenditure in healthy individuals" (1990) — The original publication of the Mifflin-St Jeor equation, the most cited BMR formula in modern nutrition science.
- Frankenfield D et al. — "Comparison of predictive equations for resting metabolic rate" (2005) — Journal of the American Dietetic Association study validating Mifflin-St Jeor as the most accurate predictive equation in non-obese adults.
- USDA Dietary Guidelines for Americans — Official US government guidance on calorie needs, macronutrient ranges, and sustainable dietary patterns.
Medical disclaimer: The results from this calorie calculator are estimates based on validated mathematical formulas. They are for informational and educational purposes only and do not replace personalized medical or nutritional advice. Individual metabolic rates vary significantly. Consult a registered dietitian, nutritionist, or healthcare professional before making significant changes to your diet, especially if you have a medical condition, history of eating disorders, are pregnant or breastfeeding, or are under 18.
