Calorie Deficit Calculator
Estimate adult maintenance calories and a daily calorie target from Mifflin–St Jeor BMR, activity level and an adjustable calorie-deficit percentage.
Calculator workspace
Enter your values, calculate, then review the assumptions shown with the result.
How this calculator helps
Estimate adult maintenance calories and a daily calorie target from Mifflin–St Jeor BMR, activity level and an adjustable calorie-deficit percentage. The calculator keeps the main answer with supporting values and the formula or method so the result is easier to check, compare and save.
How the calorie deficit calculator works
The calculator first estimates basal metabolic rate (BMR) with the Mifflin–St Jeor equation, then multiplies BMR by the selected activity factor to estimate total daily energy expenditure (TDEE), often called maintenance calories. The selected deficit percentage is then subtracted from that maintenance estimate.
Why maintenance calories are an estimate
Energy needs vary with body composition, activity tracking, training, health, hormones and individual metabolism. Activity multipliers are broad categories. Treat the number as a starting estimate that can be compared with real-world weight and intake trends over time, not as a precise prescription.
Deficit percentage
This tool allows a deficit from 1% to 30% and does not recommend a particular number. A larger mathematical deficit is not automatically appropriate or safe. Nutrition needs can be different for athletes, older adults, people with medical conditions and people taking medications.
Who should not rely on this estimator
This adult calculator is not designed for children, pregnancy, breastfeeding, eating-disorder treatment or medical nutrition therapy. In those situations, use individualized professional guidance rather than a generic energy equation.
Maintenance versus deficit
If you only want the estimated calories needed to maintain current weight, use the Maintenance Calories Calculator. This page adds the explicit deficit step because that search intent is different.
How to use it well
- Use values from the source that actually applies to your situation.
- Check units, dates, rates and percentages before calculating.
- Review the formula/method and supporting figures rather than relying only on the headline number.
- For changing rates, regulations or policies, verify the current official source before an important decision.
- Use Copy Result or Save Result Image to keep the assumptions with the answer.
Frequently Asked Questions
What is a calorie deficit?
It is an energy-intake amount below estimated maintenance expenditure. This calculator expresses it as a percentage of estimated TDEE.
Which BMR equation is used?
Mifflin–St Jeor is used, with the sex-specific constant selected in the form.
Does the calculator predict exact weight loss?
No. It estimates energy arithmetic only and does not promise a specific body-weight change.