Which BMR formula is most accurate?

The Mifflin-St Jeor equation is considered the most accurate formula for the general population, validated in a 2005 Academy of Nutrition and Dietetics review. It predicts within 10% of measured BMR for approximately 80% of individuals. The Harris-Benedict equation, while older, tends to overestimate BMR by 5%. The Katch-McArdle formula, which uses lean body mass, may be more accurate for athletic or lean individuals.

How many calories should I eat to lose 1 lb per week?

A 500 kcal/day deficit produces approximately 1 lb/week fat loss theoretically. In practice, the rate varies based on individual metabolic adaptation, water retention, and activity changes. A 250 to 500 kcal deficit is generally recommended as the sustainable range, producing 0.5 to 1 lb/week loss while minimizing muscle loss and metabolic suppression.

What is TDEE and why does it matter?

Total Daily Energy Expenditure is the total number of calories your body burns in a day across all activity, including basal metabolism, digestion, and deliberate exercise. TDEE is the number your daily calorie intake needs to be calibrated against. Eating below TDEE creates a deficit for fat loss; eating above creates a surplus for muscle gain; eating at TDEE maintains current weight.

Should I eat back exercise calories?

If you used a TDEE calculator with your activity level already factored in, exercise is already accounted for and you should not add additional calories. If you calculated BMR and used a sedentary multiplier, then yes, add a reasonable estimate for workout calories burned. Most fitness tracking apps overestimate exercise calorie burn by 20% to 50%.

Healthcare & Clinical

Calorie Needs Calculator

Estimate daily caloric needs based on age, gender, height, weight, and activity level using the Mifflin-St Jeor equation.

Medical Disclaimer

This calculator provides estimates based on the Mifflin-St Jeor equation for informational purposes only. Individual caloric needs vary based on many factors. Consult a registered dietitian or healthcare provider for personalized nutrition advice, especially if you have medical conditions.

Your Information

Age

Biological Sex

Unit System

Height (feet)

Height (inches)

Weight (lbs)

Activity Level

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Introduction

Most people guess at how much they should eat. The Academy of Nutrition and Dietetics identifies energy balance as the foundation of all weight management, yet a study published in PLOS ONE found that self-reported calorie intake underestimates actual consumption by 20% to 40% in most adults. The other direction is also common: diet apps set aggressive deficits that drop clients below their basal metabolic rate, triggering metabolic adaptation and muscle loss. Getting calorie targets right starts with an accurate BMR estimate and an honest activity multiplier. The Mifflin-St Jeor equation, recognized by the Academy of Nutrition and Dietetics as the most accurate validated formula for the general population, calculates basal metabolic rate from height, weight, age, and sex. This calculator applies Mifflin-St Jeor, adjusts for activity level using validated TDEE multipliers, and produces calorie targets for weight loss, maintenance, and muscle gain with precision.

What This Calculator Does

This calorie needs calculator computes daily calorie requirements using the Mifflin-St Jeor equation to calculate basal metabolic rate (BMR), then applies an activity multiplier to determine total daily energy expenditure (TDEE). Enter sex, age, height, weight, and activity level to receive maintenance calories, plus deficit targets for weight loss (moderate: 500 kcal deficit, aggressive: 750 kcal deficit) and surplus targets for muscle gain (lean bulk: 250 kcal surplus, standard bulk: 500 kcal surplus). Protein targets are included based on 2026 ISSN guidelines.

The Formula

BMR (Male) = 10 x weight(kg) + 6.25 x height(cm) - 5 x age + 5 | BMR (Female) = 10 x weight(kg) + 6.25 x height(cm) - 5 x age - 161 | TDEE = BMR x Activity Multiplier

The Mifflin-St Jeor equation calculates the calories required to sustain basic physiological functions at complete rest (BMR). TDEE multiplies BMR by an activity factor: sedentary (1.2), lightly active 1 to 3 days/week (1.375), moderately active 3 to 5 days/week (1.55), very active 6 to 7 days/week (1.725), and extremely active or physical job plus training (1.9). A 500 kcal/day deficit creates a theoretical 1 lb/week fat loss (3,500 kcal = 1 lb adipose tissue). Protein is set at 0.7 to 1.2 grams per pound of bodyweight depending on goal, per 2026 ISSN position stand.

Step-by-Step Example

Enter personal stats

Male, age 35, weight 190 lbs (86.2 kg), height 5'11" (180.3 cm). Select 'Moderately Active' (training 3 to 5 days per week).

Calculate BMR and TDEE

BMR = (10 x 86.2) + (6.25 x 180.3) - (5 x 35) + 5 = 862 + 1,128.75 - 175 + 5 = 1,820.75 kcal. TDEE = 1,820.75 x 1.55 = 2,822 kcal/day.

Select goal and apply calorie adjustment

Goal: moderate fat loss. Calorie target: 2,822 - 500 = 2,322 kcal/day. Expected rate: approximately 1 lb/week fat loss. Protein target at 0.9 g/lb: 171 g protein/day (684 kcal from protein).

Track and adjust after 2 weeks

After 2 weeks, if weight dropped by 1.5 to 2 lbs total, the 2,322 kcal target is working. If weight is unchanged, reduce by 150 to 200 kcal. If weight dropped more than 3 lbs, increase by 100 to 150 kcal to preserve lean mass.

Real-World Use Cases

Personal Trainer Client Onboarding

A trainer calculates initial calorie targets for a new client: female, 40, 155 lbs, sedentary office job, training 3 days/week post-program start. BMR: 1,449 kcal. TDEE (sedentary for now): 1,739 kcal. With a 400 kcal deficit: 1,339 kcal/day is below BMR, so the trainer adjusts to 1,550 kcal with the expectation that adding training activity will increase TDEE and create a natural deficit without starving the client.

Registered Dietitian Initial Assessment

A dietitian uses TDEE as the reference for a client recovering from a restrictive eating history. Rather than immediately applying a deficit, the dietitian establishes maintenance calories at 2,100 kcal, monitors metabolic response over 4 weeks, and then applies a modest 250 kcal deficit only after confirming the client is eating to maintenance without distress.

Athlete Periodization Nutrition

A competitive cyclist uses the calculator across training phases. During base season with 8 hours/week of training (very active), TDEE is 3,280 kcal. During a taper week before a race (lightly active), TDEE drops to 2,650 kcal. Adjusting intake by phase prevents unnecessary fat gain during low-intensity periods and underfueling during high-intensity blocks.

Comparison

Activity Level	Multiplier	Example TDEE (175 lbs, 5'9", Male, 30)	Weekly Training Volume
Sedentary	1.20x	2,100 kcal	Desk job, no exercise
Lightly Active	1.375x	2,408 kcal	1-3 days/week light exercise
Moderately Active	1.55x	2,715 kcal	3-5 days/week moderate training
Very Active	1.725x	3,023 kcal	6-7 days/week hard training
Extremely Active	1.90x	3,330 kcal	Physical job + daily training

Common Mistakes to Avoid

Setting calories below BMR for extended periods. Eating less than your basal metabolic rate consistently triggers metabolic adaptation (the body reduces NEAT and BMR) and accelerates muscle loss. Deficits should come from TDEE, not from sub-BMR restriction.
Using the Mifflin-St Jeor result without adjusting for individual variation. The formula has a standard error of 10%. A person with a lower-than-average metabolic rate may maintain weight at 200 kcal below their calculated TDEE. Real-world tracking over 2 to 3 weeks calibrates the estimate.
Selecting 'Extremely Active' as the activity multiplier for someone who trains hard but has a sedentary job. TDEE multipliers reflect all daily movement, not just workout intensity. A person who trains 1 hour intensely but sits for 8 hours is typically 'Moderately Active' at best.
Not adjusting calories as body weight changes. As weight decreases during a fat loss phase, BMR and TDEE decrease proportionally. Failing to recalculate every 5 to 10 lbs leads to plateaus as the original deficit disappears.

Frequently Asked Questions

Accuracy and Disclaimer

This calculator provides calorie estimates for planning purposes based on the Mifflin-St Jeor equation. Individual metabolic rates vary. These targets are starting points that should be adjusted based on real-world progress over 2 to 4 weeks. This tool is not a substitute for medical or dietetic advice. Individuals with diabetes, eating disorders, kidney disease, or other medical conditions requiring dietary management should work with a registered dietitian or physician.

Conclusion

Calorie targets are starting points. Real-world metabolic rates vary by 10% to 15% around the Mifflin-St Jeor estimate. Use your calculated TDEE for 2 weeks, track scale weight and energy levels, and adjust by 100 to 200 calories in either direction based on results. If you are working with a fitness client, pair this with the Body Fat Calculator to set composition-specific goals, and use the BMI Calculator as an additional benchmark for where current weight sits relative to healthy range.

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