Most people need 20 to 40 grams of protein after a workout to support muscle repair and recovery. That range covers the majority of body sizes and training styles, and going above 40 grams in a single post-workout sitting doesn’t appear to provide additional muscle-building benefit. But the full picture is more nuanced than a single number, and your total protein intake across the day matters more than what you eat in the hour after you rack the weights.
The 20 to 40 Gram Sweet Spot
The general recommendation from the International Society of Sports Nutrition is 0.25 grams of high-quality protein per kilogram of body weight per serving, which works out to an absolute dose of 20 to 40 grams. For a 150-pound (68 kg) person, that’s about 17 grams at the low end; for a 200-pound (91 kg) person, it’s closer to 23 grams. Rounding up to 20 to 25 grams covers most people comfortably.
Research consistently shows that about 20 grams of protein shortly after resistance exercise is enough to stimulate muscle repair. Higher single doses, over 40 grams, don’t appear to boost muscle protein synthesis any further in that immediate post-workout period. The extra amino acids are largely burned for energy or converted into waste products like urea. That said, not all of the excess goes to waste. Some of those additional amino acids still contribute to tissue-building, so eating slightly more than 20 grams isn’t harmful. It’s just not proportionally more effective.
Why Leucine Is the Real Trigger
Your muscles don’t respond to protein in general so much as they respond to one specific amino acid: leucine. Leucine acts as the biochemical switch that tells your body to shift from breaking down muscle tissue to building it back up. The threshold you need to flip that switch is roughly 2.5 to 3 grams of leucine per meal.
A typical serving of 25 to 30 grams of high-quality protein (whey, eggs, chicken, fish) contains about 2.5 to 3 grams of leucine naturally. This is one reason the 20 to 30 gram recommendation exists: it’s the amount needed to hit the leucine threshold. If you’re relying on plant-based protein sources like rice, pea, or soy, the leucine content per gram of protein tends to be lower. You may need a slightly larger serving, closer to 30 to 40 grams, to reach the same leucine threshold and get the same muscle-building signal.
The “Anabolic Window” Is Wider Than You Think
You’ve probably heard you need to chug a protein shake within 30 to 45 minutes of your last set or miss your gains. Early research did identify a post-exercise period where muscle protein synthesis is elevated, sometimes called the “anabolic window of opportunity,” estimated at roughly 45 minutes to an hour after exercise. But the practical importance of that narrow window has been significantly overstated.
A major meta-analysis found that when researchers controlled for total daily protein intake, the apparent benefit of precise post-workout timing disappeared. The groups that ate protein right after training were also eating more total protein per day (around 1.7 g/kg) than the comparison groups (around 1.3 g/kg). Once you account for that difference, timing alone had no meaningful effect on muscle gain. The muscle-building response to a single workout stays elevated for at least 24 hours, gradually tapering as time passes. So while eating protein within a couple of hours after training is reasonable, stressing over a 30-minute deadline isn’t necessary.
A practical guideline from Mass General Brigham: aim for at least 15 to 25 grams of protein within two hours after exercise. If you ate a protein-rich meal an hour or two before training, you’re already covered and the post-workout meal is less urgent.
Total Daily Protein Matters More
The single biggest factor for muscle growth and recovery isn’t your post-workout shake. It’s how much protein you eat across the entire day. Sports nutrition experts largely agree on a target of 1.6 to 2.2 grams of protein per kilogram of body weight per day to maximize muscle protein synthesis. For a 170-pound (77 kg) person, that’s roughly 123 to 170 grams spread throughout the day.
The most practical way to hit that number is to divide it across at least four meals. Research suggests a target of 0.4 grams per kilogram per meal as a minimum, up to about 0.55 grams per kilogram per meal at the higher end. For the same 170-pound person, that translates to about 31 to 42 grams per meal across four eating occasions. Your post-workout meal is just one of those four. It doesn’t need to be dramatically larger than your other meals.
Adjusting for Your Type of Training
Resistance training and endurance training place different demands on your body, and protein needs shift accordingly. If you’re lifting weights with the goal of building muscle, the higher end of the daily range (1.5 to 2.2 g/kg/day) applies. If you’re primarily doing endurance work like running, cycling, or swimming, your protein needs are slightly lower, around 1.2 to 1.6 g/kg/day, but they’re still higher than a sedentary person’s requirements.
Endurance athletes also benefit from pairing their post-workout protein with carbohydrates. A ratio of roughly one part protein to three parts carbohydrates helps replenish glycogen stores and speeds recovery, especially when the next training session is less than eight hours away. For resistance trainers, the carbohydrate pairing is less critical, though it certainly doesn’t hurt.
If you’re training to maintain existing muscle rather than build new mass, you can stay at the lower end of protein recommendations, around 1.0 to 1.2 g/kg/day. The post-workout serving still falls in the 20 to 25 gram range; you’d simply eat less protein at other meals.
Quick Reference by Body Weight
- 130 lbs (59 kg): 15–20 g per post-workout meal, 94–130 g total daily
- 155 lbs (70 kg): 18–25 g per post-workout meal, 112–154 g total daily
- 180 lbs (82 kg): 20–30 g per post-workout meal, 131–180 g total daily
- 210 lbs (95 kg): 24–35 g per post-workout meal, 152–209 g total daily
These ranges assume a goal of muscle growth using the 0.25 to 0.4 g/kg per meal guideline for the post-workout serving and 1.6 to 2.2 g/kg for the daily total. If you’re closer to maintenance mode or doing lighter exercise, the lower end of each range is appropriate.