Calorie Calculator
Estimate your daily calorie needs for weight maintenance, a calorie deficit, or a calorie surplus using the Mifflin–St Jeor equation to estimate resting energy needs.
Maintain Weight Estimate
For a 28-year-old male (175 cm, 72 kg) with a moderately active routine, the estimated daily target is 2,600 kcal.
How to use this daily target
Use the estimate as a starting baseline, then track your 7-to-14 day body-weight trend, hunger, energy levels, and training recovery to make gradual adjustments.
Illustrative Maintenance Range (±10%)
The ±10% band illustrates sensitivity around the central estimate. It is an illustrative range, not a guarantee that your true biological maintenance falls inside it.
Compare Activity Levels & Weight Goals
See how your energy requirements change across different daily physical activity tiers and caloric surpluses or deficits.
Maintenance by Activity Level
| Activity Level | Daily Calories |
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Targets by Weight Goal
| Goal Strategy | Daily Calories |
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About the Calorie Calculator
This calorie calculator estimates how much food energy an adult may need each day to maintain their current body weight. It can also show a personalized daily calorie target after applying the weight-loss (caloric deficit) or weight-gain (caloric surplus) goal you choose.
The result is a starting estimate rather than an exact measurement. Real-world energy requirements vary between individuals because no calculation can fully capture unique body composition, day-to-day non-exercise movement, occupational physical labor, illness, medications, or adaptive metabolic shifts over time.
How the calculation works: The Mifflin–St Jeor Equation
The calculator first estimates resting energy expenditure (REE) using the Mifflin–St Jeor equation. Developed in 1990 from direct metabolic measurements in 498 healthy adult men and women, the equation calculates resting energy needs from body weight, height, age, and a biological sex-specific constant:
Resting Energy = 10W + 6.25H − 5A + 5
Resting Energy = 10W + 6.25H − 5A − 161
Where W is weight in kilograms, H is height in centimeters, and A is age in years.
A systematic review conducted by the Academy of Nutrition and Dietetics comparing commonly used resting-metabolism equations found that the Mifflin–St Jeor formula predicted measured resting metabolic rate within 10% for a higher percentage of healthy non-obese and obese adults than older equations like the 1919 Harris–Benedict formula. While reliable as an initial baseline, individual metabolic rates can still differ meaningfully from formula averages.
Worked Example
Consider a 30-year-old male weighing 75 kg with a height of 180 cm:
- Weight contribution:
10 × 75 = 750 - Height contribution:
6.25 × 180 = 1,125 - Age subtraction:
5 × 30 = 150 - Sex constant:
+5 - Estimated Resting Energy (REE):
750 + 1,125 − 150 + 5 = 1,730 kcal/day
If he maintains a moderately active routine (exercise or physical work 3 to 5 days per week, corresponding to an activity factor of 1.55), his estimated maintenance calories are:
1,730 × 1.55 = 2,681.5 kcal/day (displayed as approximately 2,680 kcal/day).
From Resting Energy to Maintenance Calories (TDEE)
Resting energy accounts for only a portion of your total daily burn. The calculator multiplies your resting estimate by the activity multiplier associated with your average week. The resulting figure represents your estimated Total Daily Energy Expenditure (TDEE), commonly referred to as your maintenance calories—the amount of energy needed to keep body weight stable if intake and activity remain consistent.
Activity multipliers are broad approximations. When selecting your activity level, consider your typical whole week, including your occupation, walking, domestic chores, and purposeful exercise workouts. Because your selected activity level already factors in regular exercise, do not add workout calories back onto your daily target unless you are deliberately tracking intake and exercise separately.
Maintenance, Calorie Deficits, and Calorie Surpluses
A maintenance target reflects estimated TDEE with no goal adjustment.
- Calorie Deficit: Consuming fewer calories than your body expends prompts the mobilization of stored body fat and glycogen for energy. While public health agencies like the NHS note that creating a calorie deficit is a primary driver of weight loss, the rate of weight loss is not constant.
- Calorie Surplus: Consuming more calories than your TDEE provides the substrate needed for tissue growth and muscle hypertrophy, especially when combined with progressive resistance training.
Why weight loss is not linear: The familiar rule that a 3,500-calorie cumulative deficit yields exactly one pound of fat loss is a static model that fails over time. Research by the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) shows that as body weight decreases, metabolic rate slows and energy expenditure adapts (adaptive thermogenesis). As a result, weight-loss curves naturally taper. Use preset deficit and surplus settings as starting targets, not rigid mathematical forecasts.
How to Use Your Result & Low-Energy Diet Considerations
Treat your result as a baseline. When evaluating maintenance or weight change, track your body-weight trend over 2 to 4 weeks rather than reacting to daily scale fluctuations caused by water retention or digestive contents. If your weight changes substantially, recalculate your target using updated measurements.
If an intake target suggests severe energy restriction, exercise caution. National Institute for Health and Care Excellence (NICE NG246) guidance specifies that low-energy diets of 800–1,200 kcal/day should only be used in specific clinical weight-management contexts with professional healthcare support, while diets below 800 kcal/day require specialized medical supervision. Avoid extreme deficits that risk micronutrient deficiencies and lean muscle loss.
Who Should Not Rely on This Calculator Alone
This calculator provides a general educational estimate for adults aged 18 and older. It is not intended for growing children or teenagers, pregnant or breastfeeding individuals, people with a history of disordered eating, or individuals with medical conditions affecting metabolic function. Seek personalized guidance from a registered dietitian or licensed healthcare provider before making major dietary adjustments.
Scientific References
- Mifflin MD, St Jeor ST, Hill LA, Scott BJ, Daugherty SA, Koh YO. A new predictive equation for resting energy expenditure in healthy individuals. Am J Clin Nutr. 1990;51(2):241-247.
- Frankenfield D, Roth-Yousey L, Compher C. Comparison of predictive equations for resting metabolic rate in healthy nonobese and obese adults. J Am Diet Assoc. 2005;105(5):775-789.
- Hall KD, Sacks G, Chandramohan D, et al. Quantification of the effect of energy imbalance on bodyweight. Lancet. 2011;378(9793):826-837 (NIDDK Dynamic Model).
- National Institute for Health and Care Excellence (NICE). Obesity: identification, assessment and management. NICE Clinical Guideline [NG246]. 2023.
Health Disclaimer: This calculator provides general educational estimations based on population averages and is not medical, nutritional, or diagnostic advice. Individual metabolic rates vary due to genetics, muscle mass, thyroid function, hormonal profile, medications, and health status. Always consult a licensed healthcare professional or registered dietitian before beginning any diet or exercise program.
Frequently Asked Questions FAQs
How many calories should I eat a day?
Your daily calorie needs depend on your age, biological sex, height, weight, and physical activity level. This calculator estimates your resting energy needs using the Mifflin–St Jeor equation and scales that baseline by your typical weekly movement to estimate your Total Daily Energy Expenditure (TDEE). While public averages—such as 2,000 kcal/day for women and 2,500 kcal/day for men cited by the NHS—offer general reference points, your personalized calorie requirement reflects your unique body size and lifestyle.
What are maintenance calories?
Maintenance calories represent the amount of food energy you need to consume on average to keep your body weight stable. In this calculator, your estimated maintenance calorie level equals your Total Daily Energy Expenditure (TDEE), combining your resting energy burn with the calories burned through daily occupational movement, routine walking, and exercise.
What is the difference between resting energy, BMR, and TDEE?
Resting Energy Expenditure (REE) is the amount of energy your body burns at rest to maintain essential life functions such as breathing, blood circulation, and cellular repair. Basal Metabolic Rate (BMR) is a closely related measure recorded under strict clinical laboratory conditions after overnight fasting. Total Daily Energy Expenditure (TDEE) is higher because it combines resting expenditure with all energy burned through digestion, work, chores, and exercise across 24 hours.
What is a TDEE calculator?
A TDEE calculator estimates your Total Daily Energy Expenditure. This calculator computes resting energy first using the Mifflin–St Jeor formula and then applies an activity multiplier matching your routine. The resulting TDEE figure represents your baseline maintenance calorie requirement before any weight loss or gain adjustments.
How do I choose an activity level?
Select the option that best reflects your average whole week, rather than your single most active day. Factor in your job (desk work vs active labor), daily walking, domestic activities, and planned workouts. Because activity multipliers are broad approximations, treat the resulting figures as helpful starting ranges rather than absolute numbers.
Does the calculator already include exercise calories?
Yes. If you choose an active category (such as Moderately active for 3–5 workouts per week), your exercise burn is already factored into your maintenance estimate. Adding exercise calories back on top of your daily target counts those workouts twice and can eliminate your intended calorie deficit.
How accurate is a calorie or TDEE calculator?
A calculator provides a scientifically supported starting estimate. The Mifflin–St Jeor equation is recognized for predicting resting metabolism within 10% for a majority of healthy adults in systematic reviews. However, individual variations in body composition, thyroid function, and non-exercise activity mean your real-world energy expenditure can be higher or lower. Tracking your weight trend over several weeks provides the most reliable confirmation.
Is a 500-calorie deficit guaranteed to make me lose one pound a week?
No. While a 500-calorie daily deficit is a common benchmark, the static 3,500-calorie-per-pound rule fails to account for metabolic adaptation. As weight decreases, your body burns fewer calories at rest and during movement, causing weight loss to taper over time. Treat a 500-calorie deficit as a starting intake target rather than a guaranteed weekly timetable.
Is there a minimum number of calories everyone should eat?
There is no single universal calorie cutoff for all adults, as safe minimums depend on body size, clinical status, and medical history. National guidelines like NICE classify diets of 800–1,200 kcal/day as low-energy regimens requiring professional support, while intakes below 800 kcal/day require specialized medical supervision. If a target creates an extreme deficit, consult a healthcare provider.
Can I use pounds instead of kilograms?
Yes. Toolslight supports both Metric (cm, kg) and Imperial (feet, inches, pounds) units. You can switch between measurement systems at any time using the tabs at the top of the form, and your entered measurements convert automatically.
Why does my result differ from another calorie calculator?
Different calculators may employ different resting-metabolism equations (such as Harris–Benedict or Katch–McArdle), different activity factor definitions, or alternative rounding methods. Even when two calculators use Mifflin–St Jeor, minor variations in activity descriptions can alter estimated maintenance targets.
Should I recalculate after losing or gaining weight?
Yes. Body weight is a primary variable in the Mifflin–St Jeor formula. If you lose or gain a noticeable amount of weight, your resting energy burn and maintenance requirements change. Recalculating with your current weight ensures your daily calorie targets remain aligned with your physiological needs.
Helpful Next Steps & Related Calculations
Explore tools that naturally complement this calculation to plan your health, nutrition, and daily fitness.
- Check your adult Body Mass Index and healthy-weight boundaries with our Adult BMI Calculator.
- Need to convert height from feet and inches to centimeters or pounds to kilograms? Use our Unit Converter.
- Determine exact chronological age, days, and total hours lived with our Age Calculator.