Muscle grows across a wide spread of loads. So the useful question is not which range is best. It is which range you will run close to failure, on this lift, long enough to see it work.
A 2021 review of the repetition continuum found similar whole-muscle growth from loads of roughly 30% of your one-rep max and up, and concluded there is no ideal “hypertrophy zone.” Heavy loads still win for maximal strength. This page is how to choose a range for each exercise and then hold it.
Here is the working version. Heavy, technical lifts sit at the low end, around 5 to 8 reps. Most compound work lands between 6 and 15. Isolation work and machines are happy at 12 to 30. None of those numbers is a law, they are practice, and the next section is what the evidence does and doesn't say.
What matters more than the number is how close to failure the set ends. A range only grows muscle if the last reps are hard. That part has its own pages: whether you need to train to failure at all, and how reps in reserve measures it. This page assumes you are already working sets near the end.
Three reviews, one pattern. I checked each against its published abstract rather than trusting a summary, because rep-range claims get repeated until they stop meaning anything:
The 2021 re-examination also makes a practical case for the middle. Light loads mean many more reps, more time, and more burning discomfort that can hurt adherence. Heavy loads need more sets to match moderate ones, and heavy loads at high volume raise joint stress. It lands on moderate loads as the most efficient route, while noting that mixing ranges might help and that the evidence there is thin. Its section on muscular endurance adds that few studies on loading have been run in women.
Then hold it. Set a range per lift, progress inside it (add reps at a load until you reach the top, then add weight and drop to the bottom), and change it between blocks for a reason. How many sets per muscle group is the sister decision, and it is a separate one.
Rep ranges are easy to choose and hard to judge. Judging means setting this block's 3 sets of 8 at a given effort next to the last block's 3 sets of 12 on the same lift, and deciding which one moved. That comparison breaks the moment the range, the load or the effort goes missing from the log.
Fire Your Coach keeps the set, the load, the reps and the effort for every lift, plan against what you did, and hands them back when you plan the next block. The reasoning travels with them, so changing a range is a decision you can check later instead of a mood you had.
There is no single best one. Reviews of the loading research find similar muscle growth across a wide spread of loads, from about 30% of your one-rep max upward, when sets are taken close to failure. So pick the range by the lift. Heavier, technical lifts sit at the low end, around 5 to 8 reps. Most compound work lands around 6 to 15. Isolation work and machines tolerate 12 to 30. Then hold that range long enough to compare one block with the next.
It is a good default and not a special zone. The 2021 re-examination of the repetition continuum states there is no ideal hypertrophy zone, and that similar whole-muscle growth is available across loads of roughly 30% of 1RM and up. Eight to twelve is popular because it is efficient: heavy enough to avoid endless reps, light enough to avoid heavy joint stress at high volume.
About the same, taken near failure. Strength is different. A 2017 meta-analysis found 1RM strength gains were greater with high loads, while muscle growth was similar between low and high loads. If a heavy single matters to you, you need some heavy work. If only size matters, the load is mostly about what you can recover from and repeat.
It changes what you get from a session more than which range works. A 2021 network meta-analysis found the hypertrophy response was load independent, that untrained people grew more, and that for those with training experience, doing more sessions gave superior gains. In practice, experienced lifters judge how close a set was to failure more accurately, which is the thing that makes a lighter or heavier range work.
Assign a range to each lift, keep it for the whole block, and progress inside it: add reps at a given load until you hit the top of the range, then add load and drop back to the bottom. Change the range between blocks only when you have a reason, such as a joint that dislikes heavy loading or a lift where you want more strength. Hopping ranges every week makes the numbers impossible to compare.