Basal Metabolic Rate (BMR)
Estimate the calories your body uses at complete rest for essential functions such as breathing and circulation.
Free Health & Body Calculators
Estimate daily calorie needs, calculate BMI and healthy weight ranges, or find an exact age. Every calculation runs privately on your device.
🏥 Health & Body Tools 3 tools
BMI Calculator
Calculate your Body Mass Index and see where you fall within healthy weight ranges for your height. Supports metric and imperial units.
Calorie Calculator
Estimate your BMR, daily calorie needs (TDEE), maintenance calories, and calorie goals based on your activity level.
Age Calculator
Find your exact age in years, months, and days from any birth date, or calculate the time between any two dates.
Calorie Calculator: Estimate BMR, TDEE and Maintenance Calories
The free Calorie Calculator estimates how much energy your body uses at rest and across a typical day. Enter your age, sex, height, weight, and usual activity level in US or international units to receive input-based starting estimates.
Daily Calorie Needs (TDEE)
Apply an activity factor to BMR to estimate total daily energy expenditure and maintenance calories.
Weight Goal Starting Points
Compare example calorie targets for weight loss, weight maintenance, and gradual weight gain.
The calculator uses the Mifflin–St Jeor equation and includes five activity levels, from sedentary through extra active. Results are estimates for general planning, not medical advice or a substitute for individualized nutrition guidance.
Calculate Your Daily Calorie NeedsBMI Reference Ranges
Body Mass Index is calculated as weight (kg) ÷ height² (m²). The World Health Organization defines the following ranges for adults:
| BMI Range | Category |
|---|---|
| Below 18.5 | Underweight |
| 18.5 – 24.9 | Healthy weight |
| 25.0 – 29.9 | Overweight |
| 30.0 and above | Obese |
Health Disclaimer: MonkeyTactics health calculators are informational tools only and are not a substitute for professional medical advice, diagnosis, or treatment. BMI is a general screening tool and does not account for muscle mass, bone density, age, or sex differences. Always consult a qualified healthcare professional for personalised health guidance.
About these health calculators
MonkeyTactics health tools are designed to give you quick reference figures for common body measurements. The Calorie Calculator estimates BMR, TDEE, maintenance calories, and calorie goals from your measurements and activity level. The BMI Calculator supports both metric (kg/cm) and imperial (lbs/inches) inputs, while the Age Calculator handles any date combination — useful not just for birthdays but for calculating gestational age, medication schedules, or time-sensitive eligibility checks.
As with all MonkeyTactics tools, every calculation runs locally in your browser. No health data you enter is transmitted, stored, or shared.
Frequently Asked Questions
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What does the Calorie Calculator estimate?
It estimates basal metabolic rate (BMR), total daily energy expenditure (TDEE), maintenance calories, and example daily targets for losing, maintaining, or gaining weight. The result is a starting estimate rather than a precise prescription.
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How should I choose a Calorie Calculator activity level?
Consider your complete weekly routine, including your job, walking, household movement, and structured exercise. If you are between two activity descriptions, begin with the lower one and compare the estimate with your real-world trend.
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Is BMI an accurate measure of health?
BMI is a useful screening tool but has known limitations — it does not distinguish between fat and muscle mass, and the same BMI can mean very different things for different body types, ages, and ethnicities. Use it as a general guide, not a definitive health assessment.
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Does the BMI calculator work for children?
The standard BMI formula is designed for adults aged 18 and over. BMI for children and teenagers uses age- and sex-specific percentile charts. Consult your paediatrician for an accurate assessment for anyone under 18.
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Can the age calculator work for future dates?
Yes — the age calculator accepts any two dates, past or future, making it useful for countdowns, eligibility calculations, and planning.
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Is my health data kept private?
Yes. All calculations run entirely in your browser. No weight, height, date of birth, or any other value you enter is ever sent to a server or stored anywhere. See our Privacy Policy for details.