Anabolic Window Calculator
Get your exact post-workout protein and carbohydrate targets — personalized to your body weight, training type, and session intensity.
Anabolic Window Calculator
Post-workout protein & carb targets
Targets are based on ISSN and ACSM position stands: protein at 0.25–0.4 g/kg, carbohydrates scaled to glycogen depletion based on workout type and intensity.
Post-Workout Nutrition by Goal
| Goal | Protein post-WO | Carbs post-WO | Timing |
|---|---|---|---|
| Muscle gain | 0.3–0.4 g/kg | 0.5–0.8 g/kg | Within 1–2 h |
| Fat loss (cutting) | 0.35–0.4 g/kg | 0.3–0.5 g/kg | Within 1–2 h |
| Endurance performance | 0.25–0.3 g/kg | 1.0–1.2 g/kg | Within 30 min |
| General health | 0.2–0.3 g/kg | 0.4–0.6 g/kg | Within 2 h |
The Science Behind the Anabolic Window — What the Research Actually Says
The anabolic window refers to the post-exercise period during which the body is believed to be especially responsive to protein and carbohydrate intake for muscle protein synthesis and glycogen resynthesis. The concept originated from early resistance training research showing elevated muscle protein synthesis rates and increased insulin sensitivity in the hours immediately following exercise — suggesting that nutrient timing could meaningfully impact gains beyond total daily intake.
The scientific picture has become considerably more nuanced. Alan Aragon and Brad Schoenfeld's 2013 systematic review — and subsequent meta-analyses — found that the total daily protein and calorie intake matters far more than timing for most people in most circumstances. The post-workout "window" for muscle protein synthesis is significantly longer than originally thought: 5–6 hours of elevated anabolism post-exercise, not 30–60 minutes. The urgency of "you must eat within 30 minutes!" is overstated for individuals who ate a substantial pre-workout meal within 2–3 hours before training — that pre-workout protein still circulates and feeds muscle protein synthesis during and after the session.
Where the anabolic window becomes meaningful: fasted training (morning training with no pre-workout meal), athletes training twice per day, and glycogen-dependent performance where a second session within 4–8 hours requires maximal glycogen resynthesis. In these specific scenarios, consuming 0.3–0.4 g/kg protein and 0.5–0.8 g/kg carbohydrates immediately post-workout is supported by evidence. Otherwise, hitting your daily protein target (1.6–2.2 g/kg body weight) across 3–5 meals — with one of those meals within a few hours of training — is sufficient for maximal muscle protein synthesis. This calculator times your post-workout nutrition window based on your training schedule and last meal timing.
How Wide Is the Anabolic Window?
Earlier research suggested a narrow 30-minute window post-workout had outsized effects on muscle growth. More recent meta-analyses show that while immediate post-workout nutrition is beneficial, muscle protein synthesis remains elevated for 24–48 hours. Total daily protein intake matters most.
Best Post-Workout Food Sources
Protein: Whey isolate (fastest), eggs, Greek yoghurt, chicken breast, tuna.
Carbs: White rice, potato, banana, oats, rice cakes — fast-digesting sources replenish glycogen fastest.