Calorie Calculator

Compare 3 established BMR formulas side-by-side to choose a more informed calorie starting point

Written by PJ Last reviewed: March 2026 Method: Multi-formula comparison Methodology

Why Compare Multiple Calorie Formulas?

No single BMR formula is universally accurate. This calculator runs Mifflin-St Jeor, Harris-Benedict, and Katch-McArdle (if body fat % is provided) side-by-side, so you can see where they agree and where they diverge.

Result: An averaged calorie target across formulas, plus the individual estimates so you can choose the most relevant starting point.

  • Best for: users who want more confidence in their calorie target by cross-referencing multiple methods
  • Limitation: All formulas estimate within ±10%; track intake and body weight for 2-3 weeks to calibrate

Your Information

Units:
Metric (kg/cm)
Imperial (lb/in)
100 cm 250 cm
cm
30 kg 200 kg
kg
10 years 100 years
years
5% 50%
%
Use our Body Fat Calculator to measure
Male
Female
Sedentary
Little/no exercise
Light
1-3 days/week
Moderate
3-5 days/week
Very Active
6-7 days/week
Extremely Active
Twice daily
Weight Loss
-20% calories
Maintain
Current weight
Muscle Gain
+15% calories

Understanding Calorie Calculators

A calorie calculator estimates how many calories your body needs daily to maintain, lose, or gain weight. The calculation starts with your Basal Metabolic Rate (BMR)—the calories your body burns at complete rest—and multiplies it by an activity factor to determine your Total Daily Energy Expenditure (TDEE).

Different formulas have been developed over the years, each with its own strengths. Our calculator compares three of the most respected methods: Mifflin-St Jeor (most accurate for general population), Harris-Benedict (well-established classic), and Katch-McArdle (most accurate if you know your body fat percentage).

To get the most accurate Katch-McArdle result, calculate your body fat percentage first — it's the only formula that uses lean mass instead of total weight.

The Three BMR Formulas Explained

1. Mifflin-St Jeor (1990)

Considered the most accurate for the general population. Recommended by the Academy of Nutrition and Dietetics.

Men: BMR = (10 × weight in kg) + (6.25 × height in cm) - (5 × age) + 5
Women: BMR = (10 × weight in kg) + (6.25 × height in cm) - (5 × age) - 161

2. Harris-Benedict (1984 Revised)

Originally published in 1919 and revised in 1984. Tends to overestimate calorie needs slightly for overweight individuals.

Men: BMR = 88.362 + (13.397 × weight) + (4.799 × height) - (5.677 × age)
Women: BMR = 447.593 + (9.247 × weight) + (3.098 × height) - (4.330 × age)

3. Katch-McArdle (LBM-based)

The most accurate formula if you know your body fat percentage. Uses lean body mass rather than total weight.

Both Genders: BMR = 370 + (21.6 × Lean Body Mass in kg)
Where: LBM = Weight × (1 - Body Fat %)

Activity Multipliers

Activity Level Multipliers for TDEE Calculation
Activity Level Multiplier Description
Sedentary1.2Little to no exercise, desk job
Light1.375Light exercise 1-3 days/week
Moderate1.55Moderate exercise 3-5 days/week
Very Active1.725Hard exercise 6-7 days/week
Extremely Active1.9Intense daily training or physical job

How to Interpret Formula Differences

When two or three formulas give you different calorie targets, that's not a flaw — it reflects honest uncertainty in estimating metabolism.

The "right" number is ultimately the one that produces your expected weight change over 2-3 weeks. Formulas give you a strong starting point — your body provides the final answer.

Real-World Calorie Examples

Here's how calorie needs vary across different profiles and goals:

Weight Loss Example

Profile: Female, 30 years old, office worker

Stats: 65 kg, 165 cm, sedentary

TDEE: 1,680 kcal

Goal Calories: 1,344 kcal/day

20% deficit for steady fat loss

Maintenance Example

Profile: Male, 35 years old, gym-goer

Stats: 80 kg, 178 cm, moderate activity

TDEE: 2,767 kcal

Goal Calories: 2,767 kcal/day

Maintenance for body recomposition

Muscle Gain Example

Profile: Male, 25 years old, athlete

Stats: 75 kg, 180 cm, very active

TDEE: 3,045 kcal

Goal Calories: 3,502 kcal/day

15% surplus for lean muscle growth

Frequently Asked Questions

Which formula should I use?

For most people, the Mifflin-St Jeor formula is the best starting point. If you know your body fat percentage accurately, the Katch-McArdle formula will be most accurate. The average of all formulas is usually the safest bet for beginners.

Why do different formulas give different results?

Each formula was developed using different research populations and methodologies. Differences of 100-200 calories between formulas are normal. Mifflin-St Jeor (1990) is most accurate for average adults, while Katch-McArdle accounts for body composition.

How accurate are these calculations?

All BMR formulas are estimates based on population averages. Individual metabolism can vary by 10-15% due to genetics, hormones, and muscle mass. Use these numbers as a starting point, then adjust based on real-world results after 2-3 weeks.

What's the difference between BMR and TDEE?

BMR (Basal Metabolic Rate) is the calories your body burns at complete rest. TDEE (Total Daily Energy Expenditure) is your BMR multiplied by an activity factor. Always use TDEE, not BMR, when planning your diet.

Should I eat back exercise calories?

If you selected an activity level that includes your exercise, don't eat back additional exercise calories. If you selected "Sedentary" but exercise regularly, you can either increase your activity level or eat back roughly 50% of exercise calories.

How do I know if my calorie target is working?

Track your weight weekly for 2-3 weeks. For weight loss, expect roughly 0.25-0.75 kg/week depending on body size. For muscle gain, expect 0.25-0.5 kg/week. If progress differs significantly, adjust calories by 100-200 kcal.

Common Calorie Counting Mistakes