How your daily calorie needs are calculated
This tool first estimates your BMR (basal metabolic rate — the calories you burn at complete rest) and then multiplies it by an activity factor to get TDEE (total daily energy expenditure, the calories you actually burn on a typical day). Two formulas are supported for BMR:
If you enter a body fat percentage, the Katch–McArdle formula (which relies on lean body mass) is used automatically. Otherwise the calculator falls back to Mifflin–St Jeor, the most widely validated population-level equation.
Example
30-year-old male, 5′11″ (≈180 cm), 176 lb (≈80 kg), sedentary job, no body fat given.
- BMR (Mifflin): 10 × 80 + 6.25 × 180 − 5 × 30 + 5 = ≈1,780 kcal/day
- Sedentary factor = 1.2
- TDEE = 1,780 × 1.2 = ≈2,136 kcal/day
- Maintenance macros (30/45/25 split): ≈160 g protein, 240 g carbs, 59 g fat
- Cutting (−500): ≈1,636 kcal/day
- Bulking (+500): ≈2,636 kcal/day
Activity factors and macro split
The activity factors follow the standard U.S. dietary guidance:
| Level | Factor | Lifestyle | |---|---|---| | Sedentary | 1.200 | Office job, little to no structured exercise | | Lightly active | 1.375 | 1–3 days of walking or light training per week | | Moderately active | 1.550 | 3–5 days of moderate exercise | | Very active | 1.725 | 6–7 days of structured training | | Extra active | 1.900 | Heavy manual labor or twice-a-day training |
The macro split defaults to 30% protein, 45% carbohydrates and 25% fat (protein and carbs 4 kcal/g, fat 9 kcal/g). Adjust portions to your personal preference and the foods you actually eat.
Notes and assumptions
- US customary units: feet & inches and pounds are the default to match the North American audience. Switch the segmented controls to metric any time.
- Age limits: the input schema accepts ages 10–120. Use results for teens or seniors as rough starting points and consult a dietitian for a personalized plan.
- Cutting and bulking: −500 and +500 kcal per day are conventional rules of thumb that roughly match a 0.5–1 kg change per week. Larger or smaller deficits work too.
- Body fat entry: Katch–McArdle is only useful if your body fat estimate is reasonably accurate. If you’re unsure, leave the field blank and rely on Mifflin.
- Values you enter appear only in your browser address bar so you can bookmark or share a plan.
Frequently asked questions
Is the TDEE result accurate enough to plan meals?
It’s a good starting point. Weigh yourself weekly at the same time of day, track food for 10–14 days, and then adjust intake up or down by 100–200 kcal if the scale doesn’t move in the direction you want.
Why is my Katch BMR higher or lower than Mifflin?
Katch depends entirely on estimated lean mass. If you used a rough body fat number, try verifying it with a skinfold caliper or DEXA scan before overhauling your diet around the Katch result.
How do I adjust for pregnancy, breastfeeding or a health condition?
Don’t rely on generic formulas in those cases. Get a personalized target from a registered dietitian or your physician, then use the macro ratios as a flexible template.
Should I recalculate TDEE after losing weight?
Yes, about every 5–10 kg (10–20 lb) of change. A lighter body burns fewer calories at rest and during movement, so the original estimate will overshoot over time.