How many sets and reps should I do to build muscle?

The honest answer is that no single scheme is magic. Two things decide whether a muscle grows: that you take your sets close to failure, and that you do enough of them over a week.

On rep ranges, a 2017 meta-analysis by Schoenfeld and colleagues pooled 21 studies comparing lighter loads (up to about 60 percent of your one-rep max) with heavier loads, all sets taken to failure. Muscle growth was essentially the same across the whole spectrum. Only maximal strength clearly favoured the heavier loads. In practice that means anywhere from roughly 5 to 30 reps per set builds muscle, as long as the last few reps are genuinely hard. Sets of 8 to 12 are popular because they balance effort against time, not because the number itself is special.

What does scale growth is weekly volume. A separate meta-analysis from the same year (15 studies) found a graded dose-response: each additional set per muscle per week added about 0.4 percent more growth, and groups performing ten or more sets per muscle weekly tended to gain more than those doing fewer. The American College of Sports Medicine position stand points the same way: progressive resistance across multiple sets, not one fixed prescription.

So "3 sets of 10" is a perfectly good place to start. It is one way to reach a sensible weekly volume, not a law that the muscle obeys.

"Three sets of ten" survives because it's easy to remember and teach, and because it fits into a single column. A single number removes the paralysis of choice for a beginner, and it fits neatly as an app's default program or a magazine column. It also carries the weight of tradition: early gym culture cemented the scheme decades ago, and it has been copied ever since. There is an incentive layer too. Trainers, classes and programs sell better when they promise one correct method, and a tidy rule sounds more authoritative than "take most sets close to failure and add volume over time", which is the truer but less marketable answer.

Pick a rep range you enjoy and can push hard in, somewhere between about 5 and 30 reps, and stop each set a rep or two short of failure. Then count sets, not schemes: build up toward roughly ten hard sets per muscle group across a week, spread over two or more sessions. Add a set here and there over the months as you adapt. And remember that training only builds what you feed it. Enough daily protein is the other half of the equation.