General Medical Council UK — GMC No. 8083049 | Reviewed May 2026 | Next review: May 2027
Nutrition Tools › Calorie Calculator
Calorie Calculator (2026)
How Many Calories Do You Need? — Evidence-Based Daily Targets
Calorie needs vary far more than most people realise. Two people of identical height and weight can have metabolic rates that differ by 20% or more. This calculator uses the Mifflin-St Jeor equation — the most clinically validated formula for estimating daily calorie needs — and tells you exactly what your results mean for your health, your hormones, and your body composition goals.
Your calorie calculator
Mifflin-St Jeor formula — enter in imperial units (lbs & feet/inches)
Activity level
Goal
Your Metabolic Profile
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calories per day — —
Too lowConservativeOptimalModerateToo high
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Maintenance Calories
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kcal / day (TDEE)
Eating at this level maintains your current weight. Your BMR is — kcal — the calories your body burns at complete rest.
Fat Loss Range
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kcal / day
The evidence-based deficit range for fat loss with minimal muscle loss. Below this range, muscle breakdown accelerates significantly.
Protein Protection Target
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grams / day
Minimum daily protein to preserve muscle during your current goal. Muscle protein synthesis declines 3–8% per decade after 30 — protein intake is the primary lever.
Muscle Preservation Threshold
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kcal / day
The calorie floor below which muscle loss accelerates significantly. Eating below this level for extended periods is counterproductive for body composition.
⚠ About these results: Your calorie target is an estimate based on the Mifflin-St Jeor equation, which predicts BMR within 10% for approximately 80% of healthy adults. Individual metabolic rates vary significantly based on body composition, hormonal status, thyroid function, medications, and health conditions. A minimum of 1,200 kcal/day for women and 1,500 kcal/day for men applies as a safety floor — do not go below these thresholds without supervision from a registered dietitian or physician. Use weekly weight trends over 3–4 weeks as your real guide — daily fluctuations of 1–3 lbs are normal and do not reflect true fat loss or gain.
Free Download: Your Personalised Calorie Action Plan
Your BMR and TDEE explained, goal-specific calorie target, daily protein target by bodyweight, hormonal adjustments for perimenopause and PMOS/PCOS, the 6-step protocol, and a printable weekly tracker — all free.
Understanding Your Calorie Numbers
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BMR — Basal Metabolic Rate
The calories your body burns at complete rest. BMR accounts for 60–70% of total daily calorie expenditure and is the floor below which you should never eat for extended periods.
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TDEE — Total Daily Energy Expenditure
Your BMR multiplied by an activity factor. Eating at TDEE maintains your current weight. Eating below creates a deficit; above creates a surplus.
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Why estimates are never exact
The Mifflin-St Jeor equation predicts BMR within 10% for most people. Body composition, thyroid function, PCOS/PMOS, and perimenopause all affect actual metabolic rate in ways equations cannot fully capture.
Your Goal — What the Evidence Supports
Recomposition — lose fat and build muscle simultaneously
Maintenance caloriesHigh proteinResistance training essential
Recomposition is possible but slower than either dedicated fat loss or muscle building. It works best for people returning to training after a break, beginners, or those carrying excess body fat. Calorie target sits at or just below maintenance with protein at the high end — 1.6–2.0g per kg — to support muscle building while the deficit drives fat loss. Progress is measured by body composition change, not scale weight.
Perimenopause support — metabolic and hormonal health
Declining oestrogen from age 40 reduces insulin sensitivity, accelerates muscle loss, and shifts fat toward the abdomen. Aggressive calorie restriction during perimenopause elevates cortisol — worsening the exact abdominal fat accumulation it is trying to address. The evidence-based approach is a moderate deficit of 200–300 kcal, protein at 1.4–1.6g per kg, and resistance training 3+ times per week. This goal uses a conservative deficit that protects muscle and hormonal health.
Produces approximately 0.5 lb per week. The evidence consistently shows that moderate deficits produce better long-term body composition outcomes than aggressive restriction — less muscle loss, less metabolic adaptation, and significantly better adherence. The people who succeed with long-term weight management are rarely those who cut the most calories fastest.
Activity level check: Most people overestimate activity by one level. A desk job plus 3 exercise sessions per week = lightly active (1.375), not moderately active (1.55). A one-level overestimate adds 200–300 kcal to TDEE and can eliminate your deficit entirely. When in doubt, go lower and adjust after 2–4 weeks of real results.
Calorie Needs Across Life Stages
In your 30s
Metabolic rate declines roughly 1–2% per decade after 25. Maintaining muscle mass through resistance training is the most effective lever — muscle tissue burns approximately 3 times more calories at rest than fat tissue. Most people significantly overestimate how many calories they burn in exercise and underestimate how sedentary the rest of their day is.
In your 40s and perimenopause
Declining oestrogen reduces insulin sensitivity and shifts fat toward the abdomen. Many women find maintenance calories drop by 200–300 per day compared to their 30s. Aggressive calorie restriction during perimenopause elevates cortisol, worsening abdominal fat storage. The evidence-based response is moderate deficit, high protein, and resistance training. Read more: Cortisol and Weight Gain →
For sustainable weight loss
A 300–500 calorie deficit produces 0.5–1 lb per week and is more sustainable than aggressive restriction. Very low calorie diets accelerate metabolic adaptation and muscle loss, making weight maintenance significantly harder afterwards. The 3,500 calories = 1 lb rule is a rough estimate only — use weekly weight trends over 3–4 weeks as your real guide.
It predicts BMR within 10% for approximately 80% of healthy adults. It does not account for body composition differences, thyroid conditions, PCOS/PMOS, or hormonal changes during perimenopause. Use your result as a starting point and adjust based on real results over 2–4 weeks of accurate tracking.
Is 1,200 calories a day enough?
For most adult women, 1,200 calories is too low for sustainable daily intake. At this level it is very difficult to meet protein, micronutrient, and fibre requirements. Very low calorie diets also trigger metabolic adaptation — the body lowers its metabolic rate in response — making weight maintenance significantly harder. 1,200 calories is a clinical minimum for short-term use under professional supervision only.
Why am I not losing weight in a calorie deficit?
The most common cause is underestimating food intake — studies show people underreport calorie consumption by 20–40% even when actively tracking. Other factors include overestimating activity level, metabolic adaptation, water retention masking fat loss, hormonal factors (thyroid, PCOS/PMOS, perimenopause), and medication effects. If you have been in an accurately tracked deficit for more than 4 weeks with no change, consult a registered dietitian.
What is body recomposition and who is it for?
Body recomposition means losing fat and gaining muscle simultaneously. It is most achievable for beginners to resistance training, people returning after a break, or those carrying significant excess body fat. It requires eating at or near maintenance calories with high protein intake (1.6–2.0g per kg) and consistent progressive resistance training. Progress is measured by body composition and strength — not scale weight, which may barely move.
How should I adjust my calories during perimenopause?
Many women find maintenance calories drop by 200–300 per day during perimenopause due to declining oestrogen and accelerated muscle loss. Use a moderate deficit of 200–300 kcal maximum — aggressive restriction elevates cortisol and worsens abdominal fat accumulation. Increase protein to 1.4–1.6g per kg, add resistance training 3+ times per week, and prioritise anti-inflammatory foods. Recalculate your target every 4–6 weeks as body composition changes.
How often should I recalculate my calorie target?
Every 4–6 weeks, or after losing or gaining more than 5 lbs. As your weight changes, your BMR and TDEE change. Most plateaus happen because people continue eating at the calorie level appropriate for their old weight. Recalculate and adjust in 100–150 kcal increments based on real-world results.
Free Download: Your Personalised Calorie Action Plan
Your BMR and TDEE explained, goal-specific calorie target, daily protein target, hormonal adjustments for perimenopause and PMOS/PCOS, the 6-step protocol, and a printable weekly tracker — all free.
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Full Medical Disclaimer: This calorie calculator and all supporting content on this page is for informational and educational purposes only. It does not constitute medical advice and is not a substitute for the advice of a qualified healthcare professional. Individual calorie and nutritional needs vary significantly. Results should be treated as general estimates only. XpertVitality.com and its contributors accept no liability for any loss, injury, or damage arising from reliance on the information provided. If you have a diagnosed medical condition — including diabetes, eating disorders, kidney disease, cardiovascular disease, PMOS/PCOS, or thyroid conditions — or are pregnant or breastfeeding, consult your healthcare provider before making changes to your calorie intake. Calorie targets below 1,200 kcal for women or 1,500 kcal for men should only be pursued under medical supervision.
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