Calorie deficit calculator
Estimate your maintenance calories and a daily target for maintaining or gradually losing weight, using the Mifflin-St Jeor equation and your activity level.
Estimate your calorie needs
Use current measurements. The calculation is an estimate for adult men and is not a diagnosis or a personal prescription.
Your estimate
Enter your details and select Calculate to see BMR, estimated maintenance calories, and your target.
This is a planning estimate, not a diagnosis. Talk with a doctor or registered dietitian before making a substantial change, especially if you take medication or have thyroid, kidney, or another health condition.
Get prompt medical care for warning signs. Unexplained weight loss, a belly that is hard, swollen, or growing fast, chest pain, or breathlessness needs prompt medical attention. Do not use a calorie estimate to assess these symptoms.
How this calorie deficit calculator works
This calorie deficit calculator estimates basal metabolic rate (BMR), the energy your body uses at rest, then applies an activity multiplier to estimate maintenance calories. It uses the Mifflin-St Jeor equation for men: BMR = 10 × weight in kilograms + 6.25 × height in centimeters − 5 × age in years + 5. The original study developed and tested the equation using measured resting energy expenditure in healthy adults.1 BMR is not the same as total daily energy use: movement, work, exercise, and digestion require energy too.
For US measurements, pounds are divided by 2.20462 to get kilograms, and total height in inches is multiplied by 2.54 to get centimeters. The tool then multiplies BMR by 1.2 for sedentary activity, 1.375 for light activity, 1.55 for moderate activity, or 1.725 for very active. These standard multipliers are broad estimates, not measurements of your actual daily movement. The result rounds BMR, maintenance, and target to the nearest calorie, while the displayed arithmetic shows the underlying unrounded figures.
How to read your result
Maintenance is an estimate of the daily calories that might keep body weight broadly stable under the selected activity assumptions. The target subtracts the selected pace: zero for maintenance, about 250 calories for a slow pace, or about 500 for a moderate pace. For example, if estimated maintenance is 2,300 calories and you choose the moderate pace, the calculated target is 1,800 calories a day. These numbers are starting points to discuss and observe over time, not precise personal requirements.
The result also shows a theoretical weekly change by multiplying the selected daily deficit by seven and dividing by 3,500 calories per pound. This familiar arithmetic is only a short-term illustration. The 3,500-calorie rule overstates longer-term weight loss because energy needs and body weight change as weight is lost; dynamic models account for that adaptation.2 Actual scale weight also shifts with fluid, food, and other day-to-day factors. Do not judge a plan by a single weigh-in or expect the displayed weekly figure to repeat indefinitely.
A cautious calorie floor
This calculator will not display a daily target below 1,500 kcal. If maintenance minus the selected deficit falls below that point, it displays 1,500 and explains that the estimate was capped. This is a cautious floor chosen for this tool, not a universal biological minimum or a guarantee that the target is right for you. If the floor applies, speak with a doctor or registered dietitian before choosing a calorie target. Do not try to reach a lower number by skipping meals or making abrupt changes.
If your maintenance estimate is below the chosen pace, the calculator uses the 1,500-calorie floor. The weekly estimate is based on the deficit implied by the displayed target, not the originally selected pace, and remains a simple illustration. A maintenance result at or below the floor is a good reason to get individualized advice rather than to infer that your needs are unusually low. Height, weight, age, and activity estimates can all be entered incorrectly, so first check units and measurements.
Limits and what to discuss with a clinician
Mifflin-St Jeor predicts an average from a study equation; it does not measure your metabolism. A 2005 systematic review found that predictive equations can differ in accuracy across individuals and populations, supporting caution when treating an equation as a personal measurement.3 Age, body composition, recent weight change, daily movement, sleep, and illness can all make real needs differ from this estimate. The tool is designed for adult men and should not be used for children, pregnancy, or clinical nutrition support.
Medications and health conditions, including thyroid or kidney disease, can affect appetite, fluid balance, activity, and energy needs. Do not change medication based on this result. If weight is changing unexpectedly, or you have a condition that affects eating or metabolism, contact your clinician. Bring your recent weight trend, usual meals and drinks, activity pattern, medication list, and the calculator result. Ask what pace and monitoring approach make sense for your health and whether a dietitian would be useful.
Questions people ask
Is this a TDEE calculator?
It estimates total daily energy expenditure, often called TDEE, by multiplying estimated BMR by an activity factor. It is a rough estimate, not a direct measurement of calories burned.
What does a 500-calorie deficit mean?
It means choosing an estimated daily intake about 500 calories below estimated maintenance. The implied weekly change shown here is simplified; the 3,500-calorie rule does not account for the way energy needs adapt over time.2
Why is my target set to 1,500 calories?
The selected deficit would have produced a lower value, so this tool applies its cautious 1,500-calorie floor. It is not a personalized minimum. Discuss the estimate with a clinician or registered dietitian before acting on it.
Can I use it if I take medication or have thyroid or kidney disease?
The equation cannot account for your specific condition or treatment. Ask your clinician for individualized guidance and do not adjust medication because of a calculator result.
What if my weight does not change as expected?
Estimates, activity assumptions, intake tracking, and normal fluid variation can all affect the comparison. Review several weeks of consistent measurements with a clinician instead of making a sharp change based on one week. See our guide to why a calorie deficit may not seem to be working.
Sources: Mifflin et al., “A new predictive equation for resting energy expenditure in healthy individuals,” American Journal of Clinical Nutrition, 1990 (PMID 2305711); Hall, “What is the required energy deficit per unit weight loss?,” International Journal of Obesity, 2008 (PMID 17848938); Frankenfield et al., “Comparison of predictive equations for resting metabolic rate in healthy nonobese and obese adults: a systematic review,” Journal of the American Dietetic Association, 2005 (PMID 15883556).
This estimate cannot diagnose or treat a health condition. For a plain-language overview, see calorie deficit explained and how much of a deficit to lose a pound. Our supplement comparison guide is separate from this calorie estimate and medical care.