Use this free BMR calculator to estimate your Basal Metabolic Rate and understand how many calories your body burns at rest each day.
Free BMR calculator for men, women, weight loss, maintenance, and fitness goals.
A BMR calculator estimates your Basal Metabolic Rate, the calories your body burns at rest to maintain essential functions like breathing, circulation, and temperature regulation. It uses your age, gender, height, and weight to calculate your resting calorie needs.
Calculate BMR and your daily calorie needs in four quick steps, no signup, no math, no guesswork.
Add your age, gender, height, and weight, the four key inputs for every BMR formula.
Choose sedentary, light, moderate, active, or very active to convert BMR into TDEE.
The calculator runs the Mifflin-St Jeor formula to determine your resting calorie burn.
See your BMR, maintenance calories (TDEE), and recommended targets for your goals.
BMR, Basal Metabolic Rate, is the number of calories your body burns to stay alive while you’re completely at rest. Even if you slept all day, your body would still use this energy for breathing, circulation, brain activity, cell repair, and maintaining body temperature.
To calculate your BMR accurately, you need four inputs: age, gender, height, and weight. Each one influences your resting calorie burn in a specific way:
For most adults, BMR makes up 60–75% of total daily calorie burn. The remaining 25–40% comes from physical activity, exercise, and the thermic effect of food (digestion).
A 30-year-old woman who weighs 65 kg at 165 cm has a BMR of roughly 1,386 calories per day. A 30-year-old man at 80 kg and 180 cm has a BMR of around 1,780 calories per day. These numbers form the baseline for every nutrition and weight loss plan.
The Mifflin-St Jeor equation is the modern standard for calculating BMR. Here are the exact formulas for men and women.
For adult males:
For adult females:
Metric: 30-year-old man, 80 kg, 180 cm
BMR = (10 × 80) + (6.25 × 180) − (5 × 30) + 5 = 800 + 1,125 − 150 + 5 = 1,780 cal/day
Imperial conversion: 165 lbs ÷ 2.205 = 74.8 kg; 5’10” = 178 cm. Then run the metric formula.
The original BMR formula from 1919 (revised 1984). Still widely used, but tends to overestimate BMR slightly compared to Mifflin-St Jeor.
BMR = 370 + (21.6 × lean body mass in kg). The most accurate formula if you know your body fat percentage, preferred by lean athletes.
Understanding both numbers is essential for any nutrition plan. BMR is the foundation; TDEE is the full picture.
Makes up 60–75% of total daily calorie burn for most adults.
Calories your body burns at complete rest to keep you alive. Breathing, circulation, cell repair, temperature regulation.
This is the number you eat at to maintain your current weight.
BMR plus calories burned through activity, exercise, and digestion. TDEE equals your true maintenance calorie intake.
Sedentary (desk job, no exercise)                   × 1.2 Light activity (1–3 sessions/week)                × 1.375
Moderate activity (3–5sessions/week)               × 1.55 Very active (6–7 sessions/week)                 × 1.725
Extra active (physical job + training)                 × 1.9
To calculate maintenance calories from BMR, multiply your BMR by the activity factor that matches your real lifestyle. Be honest — most people overestimate their activity level.
To calculate calorie deficit with BMR, first find your TDEE, then subtract a deficit that matches your goal. Choose your aggressiveness based on timeline, training, and adherence.
Weight loss happens when you eat fewer calories than your TDEE. The size of the deficit determines how fast you lose weight, and how much muscle and energy you preserve along the way. Three common approaches:
Easiest to sustain. Best for body recomposition, beginners, and anyone training intensely while losing fat.
The sweet spot for most people. Steady fat loss, preserved muscle, and manageable hunger.
Faster results but higher risk of muscle loss, fatigue, and bingeing. Use only short-term.
Important rule: Never eat below your BMR for extended periods. Eating less than your resting energy demand slows metabolism, drops energy, harms sleep, and risks losing lean muscle alongside fat. Pair any deficit with adequate protein (1.6–2.2 g/kg) and resistance training to keep the weight you lose mostly fat.
Eight key variables shift your Basal Metabolic Rate, some you can change, some you can’t.
BMR drops 1–2% per decade after 20 as lean tissue declines naturally.
Men typically have higher BMRs due to more lean muscle and less body fat.
Lean muscle burns more calories at rest than fat — more muscle, higher BMR.
Larger bodies have more tissue to maintain, raising baseline calorie burn.
Thyroid, cortisol, and reproductive hormones all influence resting metabolism
Chronic sleep loss lowers BMR and disrupts hunger hormones leptin and ghrelin.
Severe under-eating drops BMR; high protein supports it through muscle preservation.
Regular training builds muscle and modestly raises BMR over the long term.
 Thirst is a late signal — by the time you feel it, you’re already mildly dehydrated. Drink steadily across the day instead.
One hour of training can cost you 500–1,500 ml of fluid. Add it to your daily total — don’t assume your base intake covers it.
Heat and humidity dramatically increase sweat losses. Plan for 500 ml – 1 L extra on hot days, even when sedentary.
Chugging more than 1 litre per hour over several hours can dilute blood sodium. Sip steadily instead.
Long workouts or hot conditions deplete sodium, potassium, and magnesium. Plain water alone may not be enough.
Sodas and energy drinks add calories and sugar that outweigh their hydration benefit. Stick to water, milk, tea, or unsweetened drinks
Six BMR calculation mistakes that derail diet and fitness plans, avoid them all.
Clear, evidence-based answers to the most common questions about calculating daily water intake.Â
A pregnancy due date calculator is usually accurate within a few days when based on a reliable last menstrual period (LMP) date. However, only about 5% of babies are born exactly on their due date, most arrive within two weeks before or after. An early ultrasound (8–13 weeks) is considered the most accurate dating method and can refine your estimated due date.
The most common method — Naegele’s rule — adds 280 days (40 weeks) to the first day of your last menstrual period. This assumes a 28-day cycle with ovulation on day 14. Adjustments are made if your cycle is longer or shorter. Alternative methods include adding 266 days to a known conception date, or using IVF transfer dates and ultrasound measurements.
Yes. A first-trimester ultrasound (between 8 and 13 weeks) is the gold standard for pregnancy dating. If the baby’s measurements differ from your LMP-based estimate by more than 5–7 days, your doctor will typically revise your due date to match the ultrasound findings. Later ultrasounds are less accurate for dating.
Yes. A first-trimester ultrasound (between 8 and 13 weeks) is the gold standard for pregnancy dating. If the baby’s measurements differ from your LMP-based estimate by more than 5–7 days, your doctor will typically revise your due date to match the ultrasound findings. Later ultrasounds are less accurate for dating.
Pregnancy is officially counted from the first day of your last menstrual period (LMP), even though conception doesn’t occur until about two weeks later. This means by the time you get a positive pregnancy test (around week 4), your pregnancy is already considered to be 4 weeks along. The full pregnancy lasts approximately 40 weeks from LMP.
Use the free Imperial Fitness Hub Water Intake Calculator to estimate your ideal daily hydration target and build a healthier routine.
Disclaimer: This calculator provides general hydration estimates only and is not medical advice. Water needs vary by health status, medication, pregnancy, breastfeeding, kidney function, and climate. Speak with a healthcare professional for personal guidance.
