What is BMR and TDEE?

BMR (Basal Metabolic Rate) is the number of calories your body burns at complete rest — just to keep organs functioning, maintain body temperature, and sustain basic biological processes. It's what you'd burn lying still in bed all day. TDEE (Total Daily Energy Expenditure) is your BMR multiplied by an activity factor — the total calories you burn in a normal day including all movement, exercise, and daily activity. TDEE = BMR × Activity Multiplier For a 30-year-old man, 80kg, 180cm: - BMR: ~1,780 kcal/day - Sedentary TDEE: ~2,136 kcal/day - Moderate activity TDEE: ~2,759 kcal/day Your TDEE is your maintenance calorie level — eat this much to maintain your weight. Eat less to lose, eat more to gain.

What is the Mifflin-St Jeor formula?

The Mifflin-St Jeor equation (1990) calculates BMR from weight, height, age and sex: Men: BMR = 10×kg + 6.25×cm − 5×age + 5 Women: BMR = 10×kg + 6.25×cm − 5×age − 161 Example — 30-year-old woman, 60kg, 165cm: BMR = 10×60 + 6.25×165 − 5×30 − 161 = 600 + 1031.25 − 150 − 161 = 1,320 kcal/day Why Mifflin-St Jeor? - Published in 1990, tested on a large diverse population - Most accurate for most people — within ±10% for 82% of subjects - Recommended by the Academy of Nutrition and Dietetics - More accurate than the older Harris-Benedict equation (1919) for modern populations Limitations: doesn't account for body composition (muscle vs fat). Leaner people burn more than the formula predicts; people with more fat burn less.

How many calories do I need to lose weight?

To lose weight, eat fewer calories than you burn (TDEE). The math: 1 pound of fat ≈ 3,500 kcal stored energy 1 kg of fat ≈ 7,700 kcal So: - 500 kcal/day deficit → lose ~1 lb/week (~0.5 kg) - 1,000 kcal/day deficit → lose ~2 lb/week (~1 kg) - 250 kcal/day deficit → lose ~0.5 lb/week Example: TDEE = 2,500 kcal - To lose 1 lb/week: eat 2,000 kcal/day - To lose 2 lb/week: eat 1,500 kcal/day Safety guidelines: - Don't go below 1,200 kcal/day (women) or 1,500 kcal/day (men) without medical supervision - 1–2 lb/week is the recommended sustainable rate - Faster loss often includes muscle loss, which slows metabolism Pro tip: prioritise protein (aim for 1.6–2.2g per kg body weight) to preserve muscle during a calorie deficit.

How accurate is this calculator?

The Mifflin-St Jeor formula predicts BMR within ±10% for approximately 82% of people. Main sources of error: 1. Body composition: The formula uses total weight, not lean mass. Two people at the same weight can have very different BMRs if one has more muscle (burns more) or more fat (burns less). If you know your body fat %, a lean-mass based formula is more accurate. 2. Activity estimation: Most people misjudge their activity level. 'Moderately active' means genuinely 3–5 workout sessions per week with moderate intensity — not 'I walk to the bus stop'. 3. Metabolic adaptation: chronic dieting, thyroid conditions, and hormonal factors affect metabolism in ways the formula can't capture. How to verify your TDEE: - Track your calories honestly for 2–3 weeks - Track your weight daily (use 7-day average) - If weight is stable, you've found your actual TDEE - Adjust the calculator's activity factor until the output matches your real TDEE

Should I use BMR or TDEE for my diet plan?

Use TDEE as your starting point, then adjust for your goal. BMR is the baseline at rest — never eat below your BMR without medical supervision (your body needs this to function). TDEE is your maintenance level — the calories that keep your weight stable. For weight loss: eat 300–500 kcal below TDEE For weight gain: eat 250–500 kcal above TDEE For maintenance: eat at TDEE Practical example: - TDEE: 2,500 kcal/day - Weight loss target: 2,000 kcal/day (−500) - Weight gain target: 3,000 kcal/day (+500) Common mistake: eating at BMR (too little) → rapid initial weight loss → muscle loss → metabolic slowdown → weight regain. Sustainable deficits of 300–500 kcal below TDEE outperform large deficits long-term. Re-calculate every 5–10 lbs of weight change, as BMR changes with body weight.

What macros should I eat for my calorie target?

Macro distribution depends on your goal: Weight loss (recommended): - Protein: 30–35% of calories (prioritise — preserves muscle) - Fat: 25–30% of calories - Carbs: 35–45% of calories Maintenance (balanced): - Protein: 20–30% - Fat: 25–35% - Carbs: 40–55% Muscle gain: - Protein: 25–30% - Fat: 25–30% - Carbs: 40–50% In grams (calorie conversion): 1g protein = 4 kcal 1g fat = 9 kcal 1g carbs = 4 kcal Example for 2,000 kcal weight loss: - 35% protein = 700 kcal ÷ 4 = 175g protein - 30% fat = 600 kcal ÷ 9 = 67g fat - 35% carbs = 700 kcal ÷ 4 = 175g carbs Minimum protein guideline: 1.6g per kg body weight (for anyone exercising). This calculator recommends macros based on your goal.

DAILY CALORIE NEEDS CALCULATOR

Calculate your daily calorie needs using the Mifflin-St Jeor BMR formula — the most accurate equation recommended by the Academy of Nutrition and Dietetics. Enter sex, age, weight (kg or lbs), and height (cm or ft/in). Select activity level from 5 options (sedentary 1.2x to extra active 1.9x). Choos...

YOUR DETAILS

Biological Sex

Used for BMR formula constants (Mifflin-St Jeor)

Age

years

Weight

= 165.3 lbs

Height

= 68.9 inches

Activity Level

Goal

YOUR RESULTS

DAILY CALORIE TARGET

2,633

kcal/day · Maintain weight

BMR (base metabolic rate)1,699 kcal

calories burned at rest

TDEE (maintenance)2,633 kcal

calories burned with activity

Target (your goal)2,633 kcal

Maintain weight

RECOMMENDED MACROS

Protein

197g

Fat

88g

Carbs

263g

ALL GOAL SCENARIOS (your activity level)

Lose 2 lb/week

1,633 kcal

Lose 1 lb/week

2,133 kcal

Lose ½ lb/week

2,383 kcal

Maintain weight

2,633 kcal

Gain ½ lb/week

2,883 kcal

Gain 1 lb/week

3,133 kcal

Gain 2 lb/week

3,633 kcal

⚠ These are estimates. Results vary based on body composition, metabolism, and health conditions. Consult a healthcare provider before significant dietary changes.

Created with❤️byeaglecalculator.com

HOW TO USE

1
Enter your biological sex, age, weight (kg or lbs — toggle between units), and height (cm or ft/in). All inputs accept decimals. The calculator converts units automatically — entering 5ft 9in converts to 175cm, entering 165 lbs converts to 74.8kg. Results update instantly as you type.
2
Select your activity level honestly — this is the biggest variable in the calculation. Sedentary (×1.2) is desk job with no exercise. Moderately active (×1.55) is the most common for people who exercise 3–5 days a week. Very active (×1.725) is daily hard training. Most people underestimate this and should start conservative.
3
Choose your goal: lose 2 lb/week to gain 2 lb/week. The calculator shows your BMR (base rate at rest), TDEE (maintenance with your activity), and target calories. The All Goal Scenarios table shows every option at once so you can compare. Click Show Formula to see the exact Mifflin-St Jeor calculation with your numbers plugged in.

FORMULA REFERENCE

MIFFLIN-ST JEOR BMR (recommended)

Men:
BMR = 10×kg + 6.25×cm − 5×age + 5
Women:
BMR = 10×kg + 6.25×cm − 5×age − 161

Published 1990. Recommended by the Academy of Nutrition and Dietetics as the most accurate for most people. Within ±10% for 82% of the population.

ACTIVITY MULTIPLIERS (PAL)

Sedentary

Desk job, little or no exercise

×1.2

Lightly active

Light exercise 1–3 days/week

×1.375

Moderately active

Moderate exercise 3–5 days/week

×1.55

Very active

Hard exercise 6–7 days/week

×1.725

Extra active

Physical job + hard training daily

×1.9

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Daily Calorie Needs · Mifflin-St Jeor BMR formula (1990) · TDEE = BMR × activity factor · Estimates only — individual metabolism varies · Not medical advice