Diet Outcome Estimator
Estimate your BMR, TDEE, and projected weight-change timeline.
How this estimate is derived
- Model:
- Mifflin-St Jeor basal metabolic rate equation
- Primary reference:
- Mifflin MD et al., American Journal of Clinical Nutrition 1990;51(2):241-247
- Implementation last reviewed:
- 2026-08-29
- Purpose:
- Educational risk estimation only; not a clinical diagnosis.
How this is calculated
This calculator uses the Mifflin-St Jeor equation for BMR, then multiplies it by an activity factor to get TDEE — your estimated total daily calorie burn. Adding your chosen calorie deficit or surplus gives your target daily intake, and the resulting weekly change (roughly 7,700 kcal per kg of body fat) projects a timeline to your goal weight.
For a complementary view of your current body composition, see the Body Fat Percentage Calculator. For general calorie burn from exercise, see the Calorie Burn Estimator. For BMI and healthy weight ranges, see the BMI Calculator.
Frequently asked questions
- What is BMR?
- Basal Metabolic Rate — the calories your body burns at complete rest just to stay alive, before any activity is added.
- What is TDEE?
- Total Daily Energy Expenditure — your BMR multiplied by an activity factor, giving your actual estimated daily calorie burn including exercise and movement.
- How many calories should I cut?
- A moderate deficit of 300-500 kcal/day produces roughly 0.3-0.5 kg (0.7-1 lb) of loss per week, which is generally considered sustainable. Larger deficits speed up loss but are harder to maintain and risk muscle loss and nutrient deficiency.
- Is a 500 kcal deficit safe?
- For most adults with a reasonable starting calorie intake, yes — but the resulting target should still stay above roughly 1,200 kcal/day (women) or 1,500 kcal/day (men), the thresholds below which it becomes difficult to meet basic nutritional needs. This calculator flags that automatically.
- What does Mifflin-St Jeor mean?
- A widely-used, well-validated equation for estimating BMR from weight, height, age, and sex, published by Mifflin and St Jeor in 1990. It is generally considered more accurate for the modern population than older equations like Harris-Benedict.
- Can I use this in my own app?
- Yes — every calculator on Stupidly Clever has a matching REST API and MCP tool that runs the same underlying logic.