BMR Calculator - Compare Mifflin-St Jeor, Harris-Benedict & Katch-McArdle
You're 35, 5'9", and 170 lb, wondering how many calories your body burns at complete rest before workouts or commuting. Mifflin-St Jeor puts your BMR near 1,700 kcal/day—compare it to Harris-Benedict and Katch-McArdle below, then layer activity for TDEE if you're planning meals.
BMR Formula Comparison
Calorie Deficit Timeline
Estimated weeks to lose 10 lbs at different deficit rates (using Mifflin-St Jeor BMR):
Methodology and limitations
Last reviewed:
Methodology
Calculates BMR using Mifflin-St Jeor, Harris-Benedict, and optionally Katch-McArdle (if body fat provided) formulas. Projects calorie deficit timelines at 0.5% and 1% weekly body weight loss rates.
Limitations
BMR formulas are population averages and do not account for individual metabolic variance, medical conditions, or adaptive thermogenesis during prolonged dieting.
Official sources
How BMR Is Calculated and Compared
You're 35, 5'9", and 170 lb, wondering how many calories your body burns at complete rest before workouts or commuting. Mifflin-St Jeor puts your BMR near 1,700 kcal/day—compare it to Harris-Benedict and Katch-McArdle below, then layer activity for TDEE if you're planning meals.
Method used
The calculator estimates BMR using Mifflin-St Jeor, Harris-Benedict, and optionally Katch-McArdle formulas. It compares results side by side and projects calorie deficit timelines for weight loss.
Mifflin-St Jeor: BMR = 10×weight(kg) + 6.25×height(cm) − 5×age + 5 (male) or −161 (female); Harris-Benedict uses different constants; Katch-McArdle uses lean mass
Practical example
A 35-year-old male, 5'9", 170 lbs has a Mifflin-St Jeor BMR near 1,696 kcal/day. A 40-year-old female, 5'4", 155 lbs on her feet all day can compare BMR to TDEE. With a 500 kcal daily deficit, 10 lbs lost takes about 10 weeks.
- Age: 35 years
- Sex: male, height: 5'9", weight: 170 lbs
- Optional: body fat percentage for Katch-McArdle
The result compares BMR across formulas, shows deficit projections for 0.5% and 1% weekly body weight loss, and includes timeline estimates.
Assumptions
- BMR formulas are population-based estimates.
- Deficit projections use 3,500 kcal per pound approximation.
- 1,200 kcal floor is enforced on deficit targets.
What this includes
- Three BMR formulas compared, optional Katch-McArdle with body fat, deficit timelines, goal weight projections.
What this excludes
- Activity multipliers (see TDEE), metabolic adaptation, medical conditions, pregnancy, athlete-specific needs, clinical diet plans.
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Frequently Asked Questions
What is BMR?
BMR, or basal metabolic rate, is the number of calories your body burns at rest to maintain vital functions like breathing, circulation, and cell production. It does not include activity.
How is BMR different from TDEE?
BMR is your resting energy expenditure. TDEE multiplies BMR by an activity factor to estimate total daily calories burned including exercise and daily movement.
Which BMR formula is most accurate?
Mifflin-St Jeor is considered most accurate for general populations. Katch-McArdle is better for athletes with low body fat since it accounts for lean mass.
Can I lose weight by eating only my BMR?
Eating at BMR creates a deficit relative to TDEE, but very low intake can slow metabolism and make adherence difficult. A moderate deficit from TDEE is usually safer and more sustainable.
Why do BMR formulas differ by gender?
Men typically have more lean muscle mass and a slightly higher metabolic rate at the same weight and height, so formulas adjust the constants by sex.