How much weight to lift: let the reps decide

"How much weight should I lift?" sounds like it should have a number for an answer. It doesn't, and not because the question is bad. The right weight depends on how many reps you're doing and how hard you're making each set, so the useful answer is a method: pick the reps, pick the effort, and let the first set tell you the weight.

This page covers choosing the weight for a set and loading your first weeks. How hard a set should feel has its own page, reps in reserve; how to keep adding weight over months is progressive overload.

Why a chart can't give you the number

The closest thing to a chart is the classic table that links a percentage of your one-rep max (the most you can lift once) to how many reps you can do with it. A 2024 meta-regression rebuilt that table from 952 tests to failure, done by 7,289 people in 269 studies; most groups were men, and most were resistance trained.¹ Two of its findings matter here:

• People differ. At 80% of a one-rep max, the spread between individuals (one standard deviation) was about 2.5 reps; at 60%, about 4.4.¹ The lighter the weight, the less a percentage tells you about your own reps.
• Exercises differ. At 80%, the estimate was about 9 reps on the bench press and 13 on the leg press.¹ In a smaller study of 16 men, eight trained and eight untrained, more reps were done at 60% of a one-rep max on the back squat than on the bench press or the arm curl.²

In both studies, training experience made little difference.^1,2 And to use a percentage at all, you'd need a tested one-rep max on every exercise, which most beginners don't have. A calculator that starts from your body weight skips the one thing that decides the weight: the reps you're about to do.

How to pick a starting weight

1. Pick the rep range. For new lifters, the American College of Sports Medicine's 2009 position stand recommends loads you can lift 8 to 12 times.³ This page uses 8 to 12 throughout.
2. Pick the effort. The ACSM's 2026 position stand says enough effort comes from sets near failure, or a target of two to three reps in reserve.⁴ New lifters leave three or four, because the guess is rougher at first (more on that below).
3. Guess light for the first working set. Choose a weight you're sure you can lift 12 times, after your warm-up sets.
4. Do the set and count. Stop at the top of the range or when you reach your reserve, whichever comes first.
5. Adjust the next set with the table below, then write the weight down so next week starts from it.

Researchers have tested this way of choosing. In an eight-week trial of 21 resistance-trained men aged 19 to 35, ten picked their own squat and bench press loads to hit a target effort, and when a set landed outside the target, the next set's load moved by 2% for every half point on the effort scale.⁵ On that scale, first tested in a 2016 study of 29 squatters, 10 means no reps left and 9 means one.⁶ Their strength and muscle thickness rose about as much as those of the other eleven, whose loads were set as percentages of a tested max.⁵ A 2022 meta-analysis of six such comparisons in resistance-trained people found similar strength gains when loads were chosen by effort or bar speed instead of fixed percentages.⁷ Both are studies of experienced lifters; for beginners, the rep range does more of the deciding.

Heavy or light: why effort matters as much as load

For muscle, a wide range of weights works when the sets are hard. A 2017 meta-analysis of 21 studies, with every set taken to failure, found similar muscle growth with light loads (60% of a max or less) and heavy ones, while heavy loads built more one-rep-max strength.⁸ The ACSM's 2026 stand, an overview of 137 systematic reviews of trials in healthy adults, found that loads from 30% to 100% of a max didn't change muscle growth, and that strength was enhanced by loads of 80% or more.⁴

The catch is that a light weight only works when you take it close to failure. In an eight-week trial of 25 untrained men, each leg trained knee extensions at 30% or 80% of a max, either to failure or stopping short. Measured as the quadriceps' cross-sectional area, the light load to failure and both heavy conditions grew the muscle; the light load stopped short didn't grow it significantly, and both heavy conditions built more strength.⁹ So the lighter the weight, the more the effort carries. That's why this page sets the weight from a rep target and a reserve, not from the number on the plate.

Your first weeks of loading

Start lighter than you think. In a study of 141 gym members, 72 men and 69 women, who each did one session of sets to failure, people underpredicted how many reps they had left: the least experienced by about four to five reps, the most experienced by about one to two.¹⁰ A 2022 review of 12 studies with 414 participants found an average miss of about one rep, smaller in sets of 12 reps or fewer, and in that review experience didn't change it.¹¹ Either way, a beginner's "two left" is often more.

That's why this site's beginner plans stop every set with three or four reps in reserve, in sets of 8 to 12: how to start lifting weights in a gym and the dumbbell plan at home. In practice:

• First session: find each weight with the steps above and write it in your workout log.
• Every session after: on any exercise where every set reached 12 with reps to spare, add the smallest step your equipment allows. Everywhere else, keep the weight and add a rep.
• Same exercises, session to session. A weight only tells you something next to last week's weight on the same lift.
• Guess easy on the effort. Your estimate gets checked every time you reach the top of the range with reps to spare.

When to add weight

The ACSM's 2009 rule: once you can do the current weight for one or two reps more than your target, add 2 to 10%.³ On a 100-pound lift, that's 2 to 10 pounds. Adding reps first is just as valid: in an eight-week trial of 43 lifters, 27 men and 16 women with at least a year of lower-body training, adding reps at the same load and adding load at the same reps were both viable, with strength slightly favoring the load group by a margin of questionable practical size.¹² How big a jump to take, and what to do when the weights stop moving, is progressive overload's job.

If the next dumbbell is too big a jump, stay at your weight and add reps past the top of the range until the heavier one fits inside it. A one-kettlebell plan progresses the same way.

Common mistakes

• Copying the person next to you. Your reserve is your own, and so is your weight.
• Testing a one-rep max to set percentages. You don't need one to start; the rep range and the reserve find the weight.
• Jumping two steps because one set felt good. Take the smallest step and let next week confirm it.
• Reaching the reps by swinging. A rep that needs a heave doesn't count toward the range. Go down a step.
• Lifting through sharp pain. That's a signal, not a rep target: stop, and see a doctor or a physical therapist.

If you'd rather not plan it alone

A rep target and a reserve will find your weight; deciding what changes when several lifts stop moving at once is the part a page can't do. Coaching is the version where your workouts are built around the days you actually have, and a weekly call looks at the week you just had and rebuilds the next one. Coaching to build muscle explains how that works, and here's how to apply. Otherwise: give your next exercise a range of 8 to 12, guess light, and let the first set tell you the weight.