BMR Calculator
Calculate calories your body burns at rest
What Is the BMR Calculator?
BMR (Basal Metabolic Rate) is the number of calories your body burns at complete rest just to maintain basic functions like breathing, circulating blood, regulating body temperature, and producing new cells. It's the foundation for estimating your total daily calorie needs, since everything else — walking, exercise, digestion, even fidgeting — gets added on top of this baseline.
For most people, BMR accounts for the majority of total daily calorie burn, often somewhere around 60-70%, which is why it matters so much for weight management. Because it can't be measured without lab equipment like indirect calorimetry, researchers developed formulas — first the original Harris-Benedict equation in 1919, later revised in 1984 — that estimate BMR from a handful of easily measured inputs: weight, height, age, and gender.
BMR is only the starting point, though. Pair it with the TDEE Calculator to apply an activity multiplier and estimate your true daily calorie needs, or use the Macro Split Calculator once you have a target calorie figure to plan out protein, carbs, and fat.
BMR Calculator Formula
Men: BMR = 88.36 + (13.4 × weight in kg) + (4.8 × height in cm) − (5.7 × age)
Women: BMR = 447.6 + (9.2 × weight in kg) + (3.1 × height in cm) − (4.3 × age)
Based on the Revised Harris-Benedict Equation.
How Is the BMR Calculator Calculated?
The equation weighs your body weight and height positively (more mass and height generally mean more calories burned at rest) and subtracts a factor for age, since metabolism tends to slow gradually over the years. Separate constants for men and women account for typical differences in muscle mass and body composition between the sexes.
This calculator uses the Revised Harris-Benedict equation (1984), which adjusted the original 1919 constants using updated population data. It remains one of the most widely used BMR formulas because it needs only weight, height, age, and gender — no body fat measurement or lab test required — though it's an estimate based on population averages rather than a direct measurement of any one person's metabolism.
BMR Calculator Example
A 30-year-old man weighing 75 kg and 178 cm tall has a BMR of 88.36 + (13.4 × 75) + (4.8 × 178) − (5.7 × 30) ≈ 1,743 kcal/day — the calories his body burns at complete rest.
A 45-year-old woman weighing 65 kg and 165 cm tall has a BMR of 447.6 + (9.2 × 65) + (3.1 × 165) − (4.3 × 45) ≈ 1,352 kcal/day, noticeably lower than the first example due to the different formula constants and the effect of age.
A 22-year-old man weighing 60 kg and 170 cm tall has a BMR of 88.36 + (13.4 × 60) + (4.8 × 170) − (5.7 × 22) ≈ 1,554 kcal/day — lower than the first example despite being younger, since his lighter body weight outweighs the age difference in the calculation.
How to Use the BMR Calculator
Step 1
Select your gender.
Step 2
Enter your age, height, and weight.
Step 3
Pick the correct height and weight units before calculating.
Step 4
Click Calculate BMR.
Step 5
View your estimated resting calorie burn and how it compares to the population average shown in the chart.
Step 6
Feed the result into a TDEE calculation once you know your typical activity level.
Benefits
- Turns your resting calorie number into a branded image you can drop straight into WhatsApp, Messages, or social apps.
- Gives a science-based starting point for setting daily calorie targets.
- Helps you understand how much of your calorie burn happens without any activity at all.
- Useful baseline before calculating TDEE for weight loss, maintenance, or gain plans.
- Free and instant, with no need for a lab-based metabolic test.
- Shows your result alongside an average BMR for your gender for quick context.
Common BMR Calculator Scenarios
Scenario 1
Setting a calorie floor you should rarely eat below for sustainable weight management.
Scenario 2
Feeding into a TDEE calculation once an activity multiplier is added.
Scenario 3
Tracking how BMR shifts over time with age, weight, or muscle gain.
Scenario 4
Sanity-checking a calorie target suggested by a diet app or nutritionist.
Scenario 5
Understanding why calorie needs differ between two people of different age, height, or gender.
Scenario 6
Establishing a starting point before planning a cut, bulk, or maintenance nutrition phase.
Understanding Your Result
Your BMR is the number of calories your body needs just to stay alive at complete rest — before any walking, exercise, or daily activity is added. It is not your total daily calorie need; for that, use a TDEE calculator that applies an activity multiplier to this number.
A BMR that looks "low" or "high" compared to the average shown in the chart isn't inherently good or bad — it mostly reflects your body size and composition. A larger frame or more muscle mass raises BMR, while a smaller frame or lower muscle mass lowers it, independent of overall health.
Tips
- Recalculate every few months, especially after meaningful weight or muscle changes.
- Use BMR as a floor, not a target — eating consistently below it is not recommended.
- Pair BMR with an activity multiplier (TDEE) for realistic daily calorie planning.
- Remember that strength training that adds muscle over time will gradually raise your BMR.
- Don't assume a low BMR means something is medically wrong — it usually just reflects a smaller body size.
Common Mistakes
- Confusing BMR with TDEE and eating only at BMR level, which ignores daily activity.
- Entering height or weight in the wrong unit without switching the selector.
- Treating BMR as a fixed number instead of recalculating after major body changes.
- Comparing your BMR directly to a friend's without accounting for differences in height, age, or gender.
- Assuming a formula-estimated BMR is exactly as accurate as a lab-measured one, when it's really a population-based approximation.
Frequently Asked Questions
What's the difference between BMR and TDEE?
BMR is calories burned at complete rest, while TDEE (Total Daily Energy Expenditure) adds your activity level on top of BMR to estimate total daily calorie needs.
Can I lose weight by eating at my BMR?
Eating below your BMR for extended periods isn't recommended, since it can slow metabolism and isn't sustainable — most weight loss plans target a moderate deficit from TDEE instead.
Does BMR change over time?
Yes, BMR generally decreases with age and can change with shifts in muscle mass, so it's worth recalculating periodically.
Why do men and women have different BMR formulas?
Men typically carry more muscle mass than women at the same weight, and muscle burns more calories at rest than fat, so the equations use different constants to reflect this.
Does muscle mass affect BMR?
Yes — muscle tissue burns more calories at rest than fat tissue, so people with more muscle mass generally have a higher BMR even at the same body weight.
Is the Harris-Benedict equation the most accurate method?
It is one of the most widely used estimation methods and reasonably accurate for most people, though methods like the Mifflin-St Jeor equation or indirect calorimetry can be more precise for specific populations.
Why is my BMR lower than a friend of the same weight?
BMR depends on age, height, gender, and body composition, not just weight — differences in muscle mass or age can lead to different BMR values even at the same weight.
Should I use my BMR to plan meals?
Use TDEE (BMR plus activity) rather than BMR alone for meal planning, since BMR only reflects resting calorie burn, not your full daily needs.
Which formula does this calculator use to estimate BMR?
It uses the Revised Harris-Benedict equation (Roza & Shizgal, 1984), one of the most widely used and validated BMR formulas, alongside the newer Mifflin-St Jeor equation.
Can I share my BMR result as an image?
Yes — tap Share and, on supported devices, your BMR is shared as a branded image card, not just a text link.
Why does my BMR go down as I get older even if my weight stays the same?
Metabolism tends to slow gradually with age, partly due to a natural decline in muscle mass over time, which is why the formula subtracts a factor based on age even when weight and height are unchanged.
Can two people with the same weight have different BMR?
Yes — height, age, and gender all factor into the calculation, so two people at the same weight can have noticeably different BMR depending on how those other factors combine.
Does exercise directly increase my BMR?
Exercise itself burns calories on top of BMR, but it can also raise BMR indirectly over time by building muscle mass, since muscle tissue burns more calories at rest than fat tissue does.
What percentage of daily calories does BMR usually make up?
For most people, BMR accounts for roughly 60-70% of total daily calorie burn, with the remainder coming from physical activity, digestion, and other non-resting energy use.
References
Important Information
Educational tool only, not medical advice.
Last updated: July 25, 2026