Precision Utility
Calorie
Calculator
Formula
Mifflin-St Jeor
Output
TDEE
Work out how many calories you need each day. Enter your age, height, weight, sex and activity level — the calculator estimates your Basal Metabolic Rate and Total Daily Energy Expenditure using the Mifflin-St Jeor equation. You'll also get personalised targets for weight loss and weight gain.
Body Parameters
Daily Energy Expenditure
2,324 kcal
Basal Metabolic Rate
1,499 kcal
Maintenance TDEE
2,324 kcal
Lose Weight (-500)
1,824 kcal
Gain Weight (+500)
2,824 kcal
How the calorie calculator works
Start by entering your age, height and weight. These three inputs feed into the Mifflin-St Jeor equation to estimate your Basal Metabolic Rate — the minimum energy your body needs at complete rest.
Next, select your sex (the formula uses different constants for males and females) and your typical activity level. The calculator multiplies your BMR by the appropriate activity factor to produce your TDEE — the total number of calories you burn in an average day.
Hit calculate and you'll see your maintenance calories, plus ready-made targets for weight loss (a 500 kcal deficit) and weight gain (a 500 kcal surplus). A 500-calorie daily deficit equates to roughly 0.45 kg of fat loss per week.
Use these numbers as a starting point, then adjust based on how your body responds over the first two to four weeks.
What you need to know about calories and TDEE
BMR vs TDEE. Your BMR covers only the basics — heart, lungs, brain, temperature regulation. It typically accounts for 60–75% of daily calorie burn. TDEE adds everything on top: walking, exercise, digestion (the thermic effect of food) and non-exercise activity like fidgeting.
Activity multipliers. The calculator uses the following factors, based on the Mifflin-St Jeor research:
- Sedentary (1.2) — desk job, minimal movement outside work
- Lightly active (1.375) — light exercise or sport 1–3 days per week
- Moderately active (1.55) — moderate exercise 3–5 days per week
- Very active (1.725) — hard training 6–7 days per week
- Extra active (1.9) — elite athlete or physical labour plus training
Safe deficit. The NHS recommends aiming for a weight loss of 0.5–1 kg per week. That translates to a deficit of roughly 500–1,000 kcal per day. Going below 1,200 kcal (women) or 1,500 kcal (men) without medical supervision is not recommended — it can slow metabolism, cause nutrient deficiencies and lead to muscle loss.
This calculator provides estimates based on population-level equations. Individual metabolism varies — track your intake and weight over several weeks and adjust your target if progress stalls.
Frequently asked questions
What is the difference between BMR and TDEE?
BMR (Basal Metabolic Rate) is the number of calories your body burns at complete rest just to keep you alive — breathing, circulation, cell repair. TDEE (Total Daily Energy Expenditure) is your BMR multiplied by an activity factor, giving you the total calories you burn in a typical day including exercise and movement.
How accurate is the Mifflin-St Jeor formula?
The Mifflin-St Jeor equation is considered the most accurate predictive formula for estimating BMR in healthy adults. Studies show it predicts measured resting metabolic rate within 10% for most people. However, individual variation exists — factors like muscle mass, genetics and metabolic adaptation can shift your actual needs.
How many calories should I eat to lose weight?
A safe and sustainable rate of weight loss is around 0.5–1 kg per week, which requires a daily deficit of roughly 500 calories below your TDEE. Going much lower than that can slow your metabolism, cause muscle loss and make the diet harder to stick to long-term.
What activity level should I choose?
Be honest — most people overestimate their activity level. Sedentary suits office workers who do little formal exercise. Lightly active covers 1–3 light sessions per week. Moderately active is 3–5 sessions. Very active is daily intense training, and extra active is for athletes or those with physically demanding jobs.
Should I eat back the calories I burn during exercise?
Your TDEE already accounts for exercise through the activity multiplier, so you generally don't need to eat back exercise calories separately. If you're using a fitness tracker that logs individual workouts on top of your TDEE, you risk double-counting. Stick to your TDEE target for consistency.
How often should I recalculate my calories?
Recalculate every 4–6 weeks or whenever your weight changes by more than 2–3 kg. As you lose or gain weight your BMR shifts, so your calorie targets need updating to keep making progress.