Leucine Threshold Calculator

About this calculator

The leucine threshold is the amount of the branched-chain amino acid leucine — roughly 2.5 to 3 grams per meal for most healthy adults — needed to maximally trigger muscle protein synthesis (MPS) through activation of the mTOR signaling pathway. Eating protein below this threshold still contributes amino acids, but it does not switch on MPS to the same degree as a dose that clears the threshold.

Research from scientists like Stuart Phillips and Donald Layman established this threshold concept, and it is why nutrition guidance for strength athletes and bodybuilders emphasizes spreading protein evenly across 3-5 meals with enough protein per sitting to clear the leucine threshold, rather than concentrating most daily protein into one or two large meals — a single high-leucine meal cannot 'carry over' its anabolic signal to a later, leucine-poor meal.

This calculator takes your leucine target and the leucine content of your chosen protein source and returns how many grams of that food you need to eat in one sitting to hit the threshold.