Switching between a bulk and a cut is not about guessing a new feed target. It is a structured shift: hold protein steady, move carbs and fat, and adjust calories by a repeatable amount.
The two adjustments
For a standard diet split, your macros change like this:
| Phase | Calories vs TDEE | Protein | Carbs | Fat |
|---|---|---|---|---|
| Cut | −15–20% | High (protect muscle) | Moderate | Moderate |
| Maintain | +0% | Steady | Base | Base |
| Bulk | +10–12% | Similar | Raised (training fuel) | Raised a little |
Where the grams actually go
On a cut, removed calories come mostly from carbs and a smaller slice of fat, while protein stays at the high end to hold onto lean mass. On a bulk, extra calories go overwhelmingly into carbs — they keep training quality high and top off glycogen. A lean person sees carbs swing by 50–100 g between phases; the protein line barely moves.
Don’t cut too fast
A deficit much beyond 20% starts costing strength, recovery and adherence. If training performance dips for more than a week, add back a portion of carbs before touching protein. Body-recomposition fans who prefer a slower approach can sit close to maintenance and let training drive the shape change.
Re-measure, don’t re-guess
Recompute when your weight or activity changes by more than a few percent. A macro calculator that takes fresh stats keeps your grams aligned with reality instead of an old plan.
The best bulk is only 10% above maintenance. The best cut is only 20% below it. Everything beyond that is survivable, not sustainable.
Set Cut, Maintain or Gain muscle in the macro calculator and the grams rebuild themselves.