Estimate resting energy
Mifflin–St Jeor: 10 × weight(kg) + 6.25 × height(cm) − 5 × age, then +5 for the male equation or −161 for the female equation.
Weight-loss calorie planning
Caloric Deficit / Weight Loss Calculator
Estimate maintenance calories, choose a modest calorie deficit, and see a transparent target intake plus a short-term energy-equivalent rate—without treating the result as a medical prescription.
Mifflin–St Jeor 5–25% guardrail Private browser calculation
Free calorie deficit calculator
Estimate a weight-loss calorie target
For adults 18+. Enter your usual body data and weekly activity, then choose a deficit between 5% and 25%. Smaller deficits are often easier to sustain and better for training performance.
Calculation method
How the calorie deficit estimate works
Estimate maintenance calories
The resting estimate is multiplied by the selected activity factor (1.2–1.9) to estimate total daily energy expenditure.
Apply your deficit
The calculator subtracts 5–25% of estimated maintenance. If the estimate falls below 1,200 kcal/day, the tool shows an extra caution rather than treating 1,200 as a universal physiological minimum.
Interpret trends, not one day
Use multi-week body-weight averages, training performance, hunger, recovery and adherence to decide whether the estimate needs adjustment.
Choosing a deficit
Smaller is not “worse,” and larger is not automatically better
A deficit that you can sustain while meeting nutrition, training and recovery needs is more useful than an aggressive number that is hard to maintain.
Gentle deficit
Useful when performance, recovery or adherence are priorities, or when you prefer a slower change.
Moderate planning range
A common starting zone for people who want a meaningful deficit without pushing toward the calculator’s upper guardrail.
Upper calculator range
More aggressive. The tool will not calculate above 25%, and lower intakes deserve more attention to nutrition adequacy and recovery.
Adjust from real data
Day-to-day scale weight reflects water, glycogen, sodium and digestion. Use longer-term averages rather than reacting to single weigh-ins.
Estimated rate of change
Why the weekly number is only a rough energy equivalent
The calculator divides the weekly calorie deficit by approximately 7,700 kcal/kg (3,500 kcal/lb) only to illustrate scale. That shortcut does not capture metabolic adaptation, changing body mass, body-composition shifts or water changes.
Weight loss is dynamic
NIDDK’s Body Weight Planner uses a dynamic mathematical model because the relationship between calorie changes and body weight changes over time.
Maintenance changes
As body weight, spontaneous movement, training and food intake change, actual maintenance calories can change too.
Scale weight is noisy
Water, glycogen, gastrointestinal contents and sodium can mask fat changes for days or weeks.
Gradual loss is easier to evaluate
CDC notes that people who lose weight at a gradual, steady pace—about 1 to 2 lb per week—are more likely to keep it off than people who lose weight faster.
Tool guide
Understand and use the Caloric Deficit / Weight Loss Calculator
Use these tool-specific notes to understand the method, enter better data, interpret the output, and apply the result appropriately.
Set Maintenance
The tool first estimates maintenance energy from resting needs and an activity factor. Because maintenance is estimated, the deficit target should be treated as a starting plan rather than an exact metabolic measurement.
Choose a Deficit
A percentage deficit scales with estimated maintenance. Smaller deficits are generally less aggressive; larger deficits create a bigger energy gap but can be harder to sustain and recover from.
Weight-Change Math
Static kcal-per-kilogram or kcal-per-pound equivalents are useful illustrations, not long-term forecasts. Real body-weight change slows and adapts over time.
Adjust From Trends
Compare several weeks of scale-weight and adherence trends before making large changes. Training performance, hunger, recovery, and nutrition adequacy also matter when deciding whether to adjust intake.
Frequently asked questions
Caloric Deficit / Weight Loss Calculator FAQs
Practical answers about this tool's inputs, method, results, limitations, and common real-world use.
What is a calorie deficit?
A calorie deficit means consuming less energy than your body uses over time. The size of the deficit is only one part of weight management; nutrition quality, protein, activity, sleep, stress and medical factors also matter.
How much of a deficit should I choose?
This tool allows 5–25%. A smaller percentage is often easier to sustain. The appropriate choice depends on body size, training load, hunger, recovery, nutrition adequacy and health context.
What if my estimate is below 1,200 calories?
The calculator does not treat 1,200 kcal/day as a universal physiological minimum. It flags very low estimated intakes for extra caution because adequacy and safe energy intake depend on individual size, health, training, medications and clinical context.
Is 3,500 calories exactly one pound of fat loss?
No. It is a simplified energy-equivalent rule and becomes inaccurate as a long-term weight forecast because energy expenditure and body composition change over time.
How often should I adjust calories?
Give a reasonable plan enough time to observe multi-week trends unless a clinician advises otherwise. Frequent day-to-day changes can make it harder to distinguish true trends from normal scale fluctuations.
Who should not use this calculator as a self-guided plan?
It is not intended for children, pregnancy or breastfeeding, eating-disorder recovery, or people whose medical conditions or medications materially affect nutrition needs. Those situations need individualized professional guidance.
Is the deficit calculated from BMR or TDEE?
It is applied to estimated total daily energy expenditure, not directly to BMR. Using BMR alone would ignore normal movement and exercise when setting the planned energy gap.
Should I add exercise calories back on top of the result?
Be careful not to count the same activity twice. If your selected activity factor already reflects regular training, automatically adding every exercise-calorie estimate can overstate energy needs.
Why is the weekly weight-change number only illustrative?
The simple energy-equivalent calculation assumes a fixed relationship between calorie deficit and body-weight change. In reality, body mass and energy expenditure adapt, so long-term change is dynamic rather than perfectly linear.
What if my real weight trend does not match the calculator?
That is common because maintenance estimates, food tracking, water balance, and activity all contain error. Use a multi-week trend to refine your working maintenance estimate instead of assuming the formula must match exactly.
Method & references
Evidence behind the calculator
The maintenance estimate uses Mifflin–St Jeor with conventional activity factors. Deficit percentages are configurable planning inputs; the page deliberately avoids claiming that a static calorie deficit predicts exact long-term weight loss.
- Mifflin MD et al. A new predictive equation for resting energy expenditure in healthy individuals.
- CDC: gradual, steady weight loss and healthy weight-management habits.
- NIDDK Body Weight Planner: personalized calorie and activity planning for adults.
- NIDDK research behind dynamic body-weight modeling.
Content reviewed: .
Weight-management disclaimer
This calculator is an educational estimate for generally healthy adults, not individualized medical or diet advice. Do not use it as a self-directed prescription during pregnancy, breastfeeding, adolescence, eating-disorder recovery, or when illness, medications or other medical conditions affect weight or nutrition. Seek qualified professional guidance when your situation is medically complex.