Calculate your fat-loss macros
Enter your details. The calculator estimates BMR with the Mifflin-St Jeor equation, multiplies by activity to get TDEE, subtracts a daily deficit sized from your loss rate (about 7,700 kcal per kg of body fat), then splits the target with protein first.
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How it works
1. BMR is estimated with the Mifflin-St Jeor equation from age, sex, weight and height. 2. An activity multiplier (1.2–1.9) gives TDEE. 3. Your daily deficit is sized from your loss rate: 7,700 kcal ÷ 7 days × your kg/week (a 0.5 kg/week rate = a 550 kcal daily deficit). 4. The target is split protein-first: protein 2.0–2.2 g/kg of body weight, fat 25% of target calories, and carbs = the remainder.
Worked example — 30-year-old woman, 70 kg, 165 cm, moderately active, 0.5 kg/week, protein 2.0 g/kg
- BMR: 10×70 + 6.25×165 − 5×30 − 161 = 1,420 kcal
- TDEE: 1,420 × 1.55 = 2,201 kcal
- Daily deficit: 7,700 × 0.5 ÷ 7 = 550 kcal/day
- Daily target: 2,201 − 550 = 1,651 kcal/day
- Protein: 2.0 × 70 = 140 g (560 kcal)
- Fat: 25% of 1,651 = 413 kcal ÷ 9 = 46 g
- Carbs: (1,651 − 560 − 413) ÷ 4 = 170 g
- Timeline: 70 → 60 kg at 0.5 kg/week = about 20 weeks
Check the arithmetic: 560 + 413 + 678 = 1,651 kcal, and 1,651 stays comfortably above the 1,200 kcal safety floor for women. Try these exact inputs in the calculator above — you should get the same numbers.
Why protein-first beats a percentage split in a deficit
Most generic macro calculators fix protein as a percentage of calories (say 30%). In a deficit that shrinks with you — at 1,400 kcal, 30% protein is only 105 g, too little to protect muscle for many people. Setting protein from body weight first (2.0–2.2 g/kg) keeps muscle protected as calories drop, which matters because a deficit can only pull energy from body fat at a limited rate; whatever energy shortfall remains comes from muscle instead.
Carbs fill the leftover calories rather than fat because carbs fuel training: people who lift or do cardio on higher carbs keep more strength and performance in a deficit, which protects the muscle that protein is defending. Fat stays at 25% — enough for hormones and vitamin absorption without eating calories that could be carbs.
Loss rates at a glance
| Rate | Daily deficit | Best for |
|---|---|---|
| 0.25 kg/week | ~275 kcal | Small deficits, beginners, people close to goal |
| 0.5 kg/week | ~550 kcal | The standard steady pace for most dieters |
| 0.75 kg/week | ~825 kcal | Larger or very active people; expect more hunger |
Deficit safety note
Do not diet below about 1,200 kcal/day (women) or 1,500 kcal/day (men) without professional supervision. Below that, getting enough protein, vitamins and minerals is hard, and muscle loss, hormonal disruption and nutrient deficiencies become real risks. This calculator shows a red warning if your target lands below the floor for your sex — treat it as a stop sign, not a suggestion, and choose a slower loss rate or check your activity input instead.
Also remember the deficit is an estimate, not a promise: BMR equations are averages, activity multipliers are guesses, and 7,700 kcal/kg is an approximation. If your weight does not move for 2–3 weeks despite hitting targets, your real TDEE is probably lower than estimated — recalculate with a lower activity level rather than slashing food further.
Interpreting your results
Daily calorie target is the number to eat — the deficit is already subtracted. Protein grams are the anchor: hit these daily, spread over 3–5 meals. Carb and fat grams are the flexible part; small daily swings are fine as long as the weekly average holds.
Your timeline assumes a constant loss rate. Real progress slows as you get lighter because TDEE falls with body weight — recalculate every 5 kg or so and expect the last stretch to take longer than the first. The scale hides fat loss behind water-weight swings for days at a time; judge a week by its average weight, not one morning.
Related calculators
Macro Calculator — daily calories, protein, carbs and fat from your body, activity and goal.
Protein Calculator — how much protein you need per day, from body weight and activity.
TDEE Calculator — your total daily energy expenditure from BMR and activity level.
BMR Calculator — your basal metabolic rate, the calories burned at complete rest.
Lean Body Mass Calculator — your lean body mass in kg plus an estimated body fat percentage.
Body Fat Calculator — estimate your body fat percentage from simple body measurements.
Pace Calculator — running pace, race time and distance from any two of the three, in km or miles.
Calorie Deficit Calculator — find your daily calorie target for weight loss, with macro grams and a goal timeline.
Diet Macro Presets — keto, low-carb, high-protein and balanced macro ratios turned into daily grams.
Best Macro Ratio for Weight Loss — guide to protein, ratios and adjusting your split in a deficit.
What Is IIFYM — explainer guide to "If It Fits Your Macros".
Macros 101 — beginner guide to protein, carbs and fat and how to start tracking.
How to Calculate Your Macros — step-by-step guide: BMR, TDEE, goal calories, protein, fat and carbs, with a worked example.
Muscle Gain Macro Calculator — lean-bulk calorie targets, surplus options and expected gain rate.
Keto Macro Calculator — keto fat, protein and net-carb grams from your calories and preset ratio.
Frequently Asked Questions
How much protein do I need to lose weight? In a deficit, about 2.0 to 2.2 g per kg of body weight per day — higher than at maintenance. This calculator defaults to 2.0 g/kg, which for a 70 kg person is 140 g of protein daily.
How fast can I safely lose weight? Around 0.25 to 0.5 kg per week is the standard sustainable pace; 0.75 kg per week suits larger or more active people. Faster rates risk muscle loss and need professional supervision.
Why did my weight loss stall? Your TDEE fell as you got lighter, food intake is under-reported, activity dropped, or water-weight swings are hiding fat loss. Recalculate targets every few weeks and track for 2–3 weeks before changing anything.
Should I cut carbs to lose weight? Cutting calories drives loss; the split affects hunger, energy and muscle. Protein-first at 2.0–2.2 g/kg with moderate carbs usually beats very low-carb for people who train, because carbs fuel workouts.
What is the lowest safe calorie intake? About 1,200 kcal/day for women and 1,500 kcal/day for men without supervision. If this calculator's warning fires, slow your loss rate — do not diet through the floor.
Does exercise change my macro targets? Exercise raises TDEE, which raises your target at the same loss rate — but workout burn is commonly overestimated. Keep the activity input honest and do not eat back extra on top of the target.
Is this medical advice? No. This is general information only. Talk to a doctor or registered dietitian before changing your diet, especially if you are pregnant, have diabetes, kidney disease, or any health condition.