BMR Calculator

BMR Calculator

Calculate your Basal Metabolic Rate (BMR) energy baseline in calories instantly using local browser memory.

Mathematical Formula & Standards

Two equations dominate BMR calculation. This tool uses Mifflin-St Jeor, which a 2005 meta-analysis in the *Journal of the American Dietetic Association* found to be more accurate than the older Harris-Benedict formula for modern populations:

1. 1Mifflin-St Jeor (This Tool):
2. 2Male: BMR = (10 * W) + (6.25 * H) - (5 * A) + 5
3. 3Female: BMR = (10 * W) + (6.25 * H) - (5 * A) - 161

Where W = weight in kg, H = height in cm, A = age in years.

1. 2Revised Harris-Benedict (for reference):
2. 2Male: BMR = 88.362 + (13.397 * W) + (4.799 * H) - (5.677 * A)
3. 3Female: BMR = 447.593 + (9.247 * W) + (3.098 * H) - (4.330 * A)

1. 3Why Mifflin-St Jeor Is Preferred: The original Harris-Benedict equation was derived from a 1919 dataset. Mifflin-St Jeor was validated on a modern population and consistently outperforms Harris-Benedict for predicting resting energy expenditure in non-obese adults.

[Age, Gender, Weight (kg), Height (cm)]
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[Mifflin-St Jeor Formula by Gender]
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[BMR in kcal/day]

Input Methodology

1. 1Select Unit System: Choose Metric (kg/cm) or Imperial (lbs/inches).
2. 2Enter Age: Your current age in years.
3. 3Select Gender: Choose male or female (affects the formula constant).
4. 4Enter Weight: Input your body weight in the selected unit.
5. 5Enter Height: Input your height in the selected unit.
6. 6Review BMR: See your estimated daily resting calorie burn rate.

BMR Calculator — Basal Metabolic Rate Estimator

Even if you lay completely still in bed all day, your body requires about 1,500 calories (for a typical adult) just to keep your heart beating, lungs breathing, and cells regenerating. This energy minimum is your Basal Metabolic Rate (BMR). Using the Mifflin-St Jeor equation, this tool calculates your baseline energy requirements before accounting for physical activity.

• BMR Seems Extremely Low (Under 1,000 kcal): Verify height is entered in centimetres (not metres) and weight in kilograms (not grams).
• Imperial Result Differs from Expectations: The tool converts lbs to kg (÷2.2046) and inches to cm (×2.54) internally. Verify inputs are in the correct units.
• Results Not Updating: Clear browser cache and reload the page.

How does BMR change with age?

BMR typically decreases by approximately 1–2% per decade after age 20, primarily because lean muscle mass tends to decline with age (sarcopenia). This is why calorie needs often decrease even if lifestyle remains unchanged.

Does having more muscle increase BMR?

Yes. Skeletal muscle tissue burns approximately 13 kcal/kg/day at rest, while fat tissue burns only 4.5 kcal/kg/day. Individuals with higher lean muscle mass have proportionally higher BMR values.

What is the difference between BMR and RMR?

BMR (Basal Metabolic Rate) is technically measured under strict fasting and resting conditions (no food for 12 hours, fully at rest). RMR (Resting Metabolic Rate) is measured under less strict conditions and is typically 10–20% higher than true BMR. Most online calculators — including this one — estimate RMR, not strict BMR, though the terms are often used interchangeably in fitness contexts.

Is my health data stored anywhere?

No. All calculations run client-side in your local browser. Your inputs are never uploaded.

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