TDEE Calculator
Estimate your daily calorie needs with Mifflin-St Jeor or Katch-McArdle formulas. Protein targets and medication-aware guidance for GLP-1, TRT, and HRT users.
Light exercise 1-3 days/week
Enables the more accurate Katch-McArdle formula
Adjusts calorie and protein guidance
Maintenance (TDEE)
Calories to maintain current weight
Deficit (-500)
~1 lb / 0.45 kg loss per week
Surplus (+300)
Lean bulk — minimal fat gain
Protein Target
0.7-1.0g per lb bodyweight
Basal Metabolic Rate (BMR)
Calories burned at complete rest — your body's baseline
How TDEE Works
Your Total Daily Energy Expenditure (TDEE) is the total number of calories your body burns in a day. It combines your Basal Metabolic Rate (BMR) — the energy your body needs just to exist — with the calories burned through daily activity and exercise.
BMR accounts for roughly 60-70% of your total energy expenditure. It covers breathing, circulation, cell repair, and maintaining body temperature. The remaining 30-40% comes from physical activity and the thermic effect of food (energy used to digest what you eat).
Mifflin-St Jeor vs Katch-McArdle
Mifflin-St Jeor (1990)
Uses weight, height, age, and sex to estimate BMR. The most widely validated formula for the general population. More accurate than the older Harris-Benedict equation.
Male: 10 x kg + 6.25 x cm - 5 x age - 5
Female: 10 x kg + 6.25 x cm - 5 x age - 161
+ No body fat measurement needed
- Less accurate for very muscular or very lean people
Katch-McArdle
Uses lean body mass only — which means it accounts for muscle-to-fat ratio directly. More accurate for people who know their body fat percentage, especially those with above-average muscle mass (like TRT users).
BMR = 370 + 21.6 x lean mass (kg)
+ More accurate when body fat % is known
- Requires body fat % input (which itself is an estimate)
TDEE and Medications
GLP-1 Users
GLP-1 medications (semaglutide, tirzepatide) significantly suppress appetite. Many users unknowingly eat far below their deficit target, which can accelerate muscle loss. Track your intake to ensure you're hitting protein targets — even if you're not hungry.
TRT Users
Testosterone increases BMR slightly by supporting higher muscle mass. Standard TDEE calculators may underestimate your needs if you've gained significant lean mass. Consider using Katch-McArdle with a recent body fat % measurement for better accuracy.
HRT Users
Hormone therapy gradually shifts body composition. Estrogen-based HRT tends to redistribute fat, while testosterone-based HRT may increase muscle mass. Recalculate TDEE every 3-6 months as your body changes.
Frequently Asked Questions
How accurate is this calculator?+
TDEE calculators are estimates — typically within 10-15% of your actual expenditure. Use the result as a starting point, then adjust based on real-world weight trends over 2-3 weeks. If you're not losing weight at the deficit number, reduce by another 100-200 kcal.
Should I eat back exercise calories?+
Your activity level multiplier already accounts for exercise. Eating back additional 'exercise calories' (like those estimated by a smartwatch) often leads to overeating because calorie burn estimates from wearables are notoriously inaccurate — often off by 30-50%.
Why does sex matter for the formula?+
The Mifflin-St Jeor formula uses biological sex because average body composition differs — specifically, the typical ratio of muscle mass to fat mass at the same weight. This affects BMR. If you know your body fat %, the Katch-McArdle formula skips sex entirely and uses lean mass directly.
What's the difference between BMR and TDEE?+
BMR (Basal Metabolic Rate) is the energy your body burns doing absolutely nothing — lying in bed all day. TDEE (Total Daily Energy Expenditure) adds your physical activity on top. You should never eat below your BMR long-term.
Is a 500 calorie deficit safe?+
For most people, a 500 kcal daily deficit produces roughly 1 lb (0.45 kg) of fat loss per week, which is generally considered safe and sustainable. Larger deficits risk muscle loss, metabolic adaptation, and nutrient deficiencies — especially on GLP-1 medications where appetite is already suppressed.
How much protein do I actually need?+
Research consistently supports 0.7-1.0g per pound of bodyweight (1.6-2.2g per kg) for people who are active and/or trying to preserve muscle during weight loss. On GLP-1 medications, lean toward the higher end. The RDA of 0.36g per pound is a minimum to prevent deficiency, not an optimal target.
Why does this calculator show a +300 surplus instead of +500?+
A +500 surplus was the old bodybuilding standard, but research shows that most of the extra calories beyond +300 are stored as fat rather than used for muscle growth. A lean bulk at +300 supports muscle gain with minimal unnecessary fat accumulation.
How often should I recalculate my TDEE?+
Recalculate every 10 lbs (4.5 kg) of weight change, or every 3 months if your body composition is shifting (common on TRT or HRT). Your TDEE decreases as you lose weight because there's less body mass to fuel.
Data Sources
- Mifflin, M.D. et al. (1990) — "A new predictive equation for resting energy expenditure in healthy individuals." American Journal of Clinical Nutrition, 51(2), 241-247
- Katch, F.I. & McArdle, W.D. — Lean body mass-based BMR estimation formula
- Morton, R.W. et al. (2018) — "A systematic review of protein requirements for muscle gain." British Journal of Sports Medicine, 52(6), 376-384
- Slater, G.J. et al. (2019) — "Is an energy surplus required to maximize skeletal muscle hypertrophy?" Frontiers in Nutrition
Related Tools
Track your nutrition in the Doseline app — log weight daily, see calorie trends over time, and get medication-aware insights that adapt as your body changes.
Doseline provides informational tools only. It is not a medical device and does not provide medical advice. Always consult a qualified healthcare provider.
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