How the cut or bulk calculator works
The decision logic
Body-fat context decides: cut when estimated body fat is above ~15% (men) / ~25% (women) — surplus calories land more on fat than muscle up there. Lean bulk when below ~12% / ~22% — the zone where muscle gain outpaces fat gain. Maintain or recomp in between, especially for newer trainees who can do both at once.
Timelines that respect math
The calculator computes weeks-to-target from your preferred rate: 0.5 kg/week is the classic cut pace (deficit ≈ 500 kcal), 0.25–0.3 kg/week the lean-bulk pace (surplus ≈ 250–300). Long phases break adherence — if the timeline exceeds ~16 weeks, plan a maintenance diet break of 1–2 weeks in the middle. Physics sets the floor on speed; psychology sets the sustainable pace.
Estimating body fat without a DEXA
Visual references beat bathroom scales: BIA scales err ±5–8% and track trends only. Use comparison photos against validated reference charts, or the US Navy tape method (±3–4%) — the calculator's job works with an honest estimate, and the mirror-plus-trend beats any single measurement.
The transition nobody plans
Ending a cut at 2,000 kcal and returning to 3,000 immediately guarantees rebound: metabolic adaptation plus lost NEAT plus hunger overshoot. Reverse up gradually (+100–150 kcal/week until TDEE) and hold at maintenance for 4–8 weeks before bulking. The calculator includes the maintenance bridge in its plan.