Weighted 1RM calculator

Strength training runs on a simple promise: know your one-rep max and you know exactly how much to load. Calisthenics breaks that promise. On a pull-up or a dip you are not loading a bar, you are moving your own body, and the plate hanging from your waist is only the visible part of the load. This tool fixes the arithmetic: it adds your bodyweight to the added weight, runs the total through four classic formulas, and tells you how much extra weight you could pull or push for a single rep.

Why bodyweight changes the maths

A 1RM calculator built for barbells starts from the weight on the bar. That works because the bar is the whole load. On a weighted pull-up, the bar is not the load at all. If you weigh 72 kg and hang 20 kg from your waist, the muscles have already moved 72 kg before the plate is added. The real load at the bottom of the rep is 92 kg, and that is the number the formulas need.

Skip that step and the result is nonsense. Feed 20 kg into Epley for five reps and it answers that your 1RM is 23 kg, as if your body weighed nothing. The honest answer is roughly 105 kg of total load, which is about 33 kg of added weight on top of your bodyweight. That added-weight figure is the one you can act on: it tells you what to hang from the belt on a max attempt, and it is why this calculator reports two numbers instead of one.

The same logic covers the barbell exercises. For a back squat, bench press or deadlift there is no bodyweight to add, so the tool uses the weight on the bar, bar included. One model, two cases, no separate calculators to keep in sync.

The four formulas

No single formula predicts a 1RM perfectly. Each was fitted to a different data set, with different exercises, rep ranges and athletes, so each carries its own bias. Showing all four is not indecision; it is the only honest way to present an estimate.

Epley is the most common in gym apps: one-rep max equals load times one plus reps divided by thirty. It is simple and reliable in the mid rep ranges. At low reps it tends to read a little high; because it grows linearly, Brzycki and Lander overtake it from around ten reps.

Brzycki uses a simple fraction: load times thirty-six, divided by thirty-seven minus reps. It is the lowest of the four at low reps, but its curve climbs faster and faster and catches Epley at around ten reps. As the rep count approaches thirty-seven the denominator heads towards zero and the result explodes, which is why this tool drops it from 29 reps.

Lombardi raises the rep count to a small power instead of scaling linearly. That makes it flatter than Epley: it does not inflate as fast, it behaves well when the set is short, and at high reps it is the lowest of the four.

Lander uses a denominator that shrinks as reps rise, similar in spirit to Brzycki. In practice it tracks Brzycki closely: slightly above it at low reps and almost identical at high reps. It shares the same limit too, so the tool drops it from the same 29 reps.

When the four land close together you can trust the middle of the range. When the result varies a lot, the disagreement is information: your rep count is far enough from a single rep that the extrapolation is doing heavy lifting. Testing closer to your max always tightens the result.

Turning a rep max into a range

The tool does not pretend there is one true number. It shows the average of the four estimates as a headline, then the full range beneath it. For the athlete weighing 72 kg who did five weighted pull-ups with 20 kg, the four formulas land between roughly 103.5 and 108 kg of total load. That is a range of about 5 kg, or two plates, which is a realistic picture of the uncertainty.

For bodyweight movements the tool also converts every estimate back into added weight. Subtract the bodyweight from the total and you get the extra weight that corresponds to the estimate. The average says around 33-34 kg of added weight for one rep; the range says it could be anywhere from about 31 to 36 kg. If you have never tested a weighted pull-up before, that range is enough to pick a starting attempt without guessing.

One special case is worth calling out. If you tell the tool you did a single rep, it does not estimate anything: a single rep is a real max, so the answer is the load you actually used. That keeps the tool from inflating a max attempt the way a raw formula would.

Reading the programming table

The percentage table is where the estimate becomes a plan. Each row is an intensity, from 100% down to 60% of your 1RM, with the reps usually associated with that intensity next to it. Under the hood, every percentage is applied to each formula's own 1RM, so each column is a different opinion about the same session.

That is more useful than it sounds. If you are running a heavy strength block at 85% for around five or six reps, you can read the four columns and pick the load you trust. If you are doing volume work at 65% for high reps, a wide spread between columns is a reminder that the maths gets softer as reps rise, so it pays to be conservative.

For bodyweight exercises, every cell shows two numbers: the added weight in bold and the total load in small print. The added weight is what you actually add to the belt; the total is what your muscles feel. When the added weight would be zero, the movement is a plain bodyweight rep at that intensity. When it would be negative, that intensity sits below your bodyweight: you would need assistance, such as a band, or an easier variation. Either way the table says so instead of printing a meaningless number.

Programming around your estimate

The estimate is a starting point, not a verdict. Use it to set your first working weights, then adjust from what actually happens in the session. If 85% feels easy for the prescribed reps, the estimate was low; if you can barely finish, it was high. A few weeks of honest feedback will teach you more than any formula.

Keep the added-weight progression gradual. A common approach is to add small jumps, a kilogram or two, once you can complete all the prescribed reps with one or two in reserve. Chase quality reps over ego lifts: a weighted pull-up with a half range and a swinging body teaches nothing and invites injury.

A note on safety

A 1RM is a maximum by definition, and maximums are where technique breaks first. Leave a margin on your true max, warm up thoroughly, and never test a heavy single without a spotter or a safe setup. The tools here are orientative and are not medical advice. If something hurts, stop and see a doctor or physiotherapist before you chase a number.

If you are new to weighted calisthenics, treat the estimate as a ceiling to approach over months, not a target for next week. Build the base, log your reps, and let the numbers converge as you get stronger.