Cutting Calorie Calculator
A cutting calorie calculator for losing fat without losing muscle. It starts from your Mifflin-St Jeor TDEE, applies a 15–25% deficit you control, keeps protein at the muscle-sparing 1.6–2.2 g/kg range, and flags minimum safe calorie floors so the cut stays sane.
Result
| BMR (Mifflin-St Jeor) | |
| Activity multiplier | |
| Deficit | |
| Protein target | |
| Safety check |
Formula & source
Cutting target = TDEE × (1 − deficit%)
Protein = 1.6–2.2 g per kg body weight (muscle-sparing)
Safety floor flagged at 1500 kcal/day
Sources: Mifflin-St Jeor (1990) for TDEE; ISSN protein range (Jäger et al., 2017) — protein stays high during cuts to protect lean mass, which multiple trials confirm reduces muscle loss in a deficit. The 1500 kcal flag is a conservative sanity threshold, not a medical prescription. Unique to this page: the safety check is computed, not buried in fine print.
Worked example (you can verify by hand)
Input: same male (TDEE 2763), 20% deficit, 81.65 kg.
- Target = 2763 × 0.80 = 2210.4
- Protein = 130.6 to 179.6 g/day (unchanged — deficit comes from carbs/fat)
- Safety: 2210 > 1500 ✓
Expected output: ≈ 2210 kcal/day; protein 131–180 g/day.
Limitations — what this cannot do
- Equations estimate population averages — individual metabolism varies ±10–15%; treat output as a starting point and adjust from 2–3 weeks of scale and mirror data.
- Activity multipliers are the largest error source; be honest about training volume or the number is fiction.
- This is nutrition math, not medical advice — see the disclaimer below.
- Very aggressive deficits cost muscle and adherence — a slower cut you finish beats a brutal one you quit.
- If you have a history of disordered eating, do not self-prescribe deficits — work with a professional.
Disclaimer: Estimates for training planning only, not medical advice. Consult a professional.
FAQ
How fast should I lose weight on a cut?
About 0.5–1% of body weight per week. Faster usually means meaningful muscle loss unless you are very overweight, where 1%+ can be fine.
Should protein stay high while cutting?
Yes — that is the single most evidence-backed lever for keeping muscle in a deficit. Keep 1.6–2.2 g/kg and cut carbs and fat instead.
Do I need cardio to cut?
No — the deficit does the work and can come from diet alone. Cardio helps adherence and work capacity, but out-training a bad diet is a myth for most people.
When should I end the cut?
When you hit the goal, when strength has stalled for weeks, or when adherence collapses — whichever comes first. Then reverse-diet back up slowly.