One Rep Max Calculator
Estimate your one-rep max (1RM) from a set of several reps using the Epley, Brzycki, and Lombardi formulas, with a training-percentage table for every rep range.
Cómo usar esta calculadora
- 1Enter the weight you lifted and how many reps you completed to near failure.
- 2Choose pounds or kilograms.
- 3Read the estimated one-rep max, averaged across the standard formulas.
- 4Use the percentage table to pick training weights for strength or hypertrophy.
Cómo funciona
One-rep max estimates
Epley: 1RM = w × (1 + reps ÷ 30) Brzycki: 1RM = w × 36 ÷ (37 − reps) Lombardi: 1RM = w × reps^0.10 w = weight lifted for the given reps
A one-rep max is the heaviest weight you can lift for a single repetition of an exercise, and it is the standard yardstick of strength. Testing it directly is risky and taxing, so strength coaches estimate it from a submaximal set instead: lift a lighter weight for several clean reps to near failure, and a formula projects what a single all-out rep would be. The best-known formulas — Epley, Brzycki, and Lombardi — were each fitted to real lifting data and agree closely in the low-rep range. Averaging them smooths out their individual quirks. From the estimated max, standard percentages then prescribe the loads for different training goals, from heavy low-rep strength work to lighter high-rep hypertrophy.
Ejemplo resuelto
Lifting 185 lb for 5 clean reps gives an Epley estimate of 185 × (1 + 5/30) ≈ 216 lb, a Brzycki estimate of 185 × 36 ÷ 32 ≈ 208 lb, and a Lombardi estimate of about 217 lb — averaging to roughly 214 lb. Training percentages then follow: about 160 lb for sets aimed at muscle growth (75%).
One Rep Max Calculator: la guía completa
Why estimate rather than test a true max
A genuine one-rep max attempt is the most demanding thing you can do in a gym: it loads the joints and nervous system to their limit, carries a real risk of injury if form breaks, and needs an experienced spotter for lifts like the bench press. It is also unnecessary most of the time. Because the relationship between reps and load is highly predictable, a set of five or eight reps with a manageable weight reveals your max nearly as accurately as grinding out a true single, with none of the danger.
This is why almost all strength programming is built on estimated maxes. Coaches take a recent hard set, run it through a formula, and prescribe the next block of training as percentages of the result. Retesting is then just a matter of doing another submaximal set and recalculating, so progress can be tracked continuously without ever risking a maximal attempt. The estimate is not a poor substitute for a real max — for planning purposes it is the preferred tool.
Why the formulas disagree, and when they're accurate
The Epley, Brzycki, and Lombardi formulas were each derived by fitting curves to observed lifting performance, and they encode slightly different assumptions about how quickly strength falls off as reps rise. In the low-rep range — say two to ten reps — they land within a few percent of one another, which is why averaging them gives a robust figure. As the rep count climbs into the high teens, they diverge more, and all of them become less reliable.
The reason is that a high-rep set stops being a pure test of maximal strength and starts measuring muscular endurance, which varies far more between people. Someone with a high proportion of slow-twitch fibres can crank out many reps at a given percentage of their max, while a more explosive lifter fatigues faster. No single formula can capture that spread. The practical takeaway is to base your estimate on a set of roughly two to eight reps, where the prediction is tightest.
Turning a max into a training plan
The real value of knowing your one-rep max is that it turns vague effort into precise programming. Different goals live at different percentages of the max: work above about 85% builds maximal strength and is done for low reps; the 65–80% band drives muscle growth at moderate reps; and lighter loads below 60% build endurance and are useful for technique practice and warm-ups. The percentage table above translates your estimated max straight into these training loads.
Using percentages keeps training honest as you get stronger. Rather than guessing weights, you anchor each session to a fraction of a number that itself climbs over time, so the loads rise automatically as you progress. Periodised programs cycle through these percentages deliberately — building volume at moderate loads, then peaking at high ones — which is only possible when you have a reliable max to work from. Recalculate every few weeks from a fresh test set and the whole plan updates with you.
Preguntas frecuentes
How is one-rep max calculated?
From a submaximal set: you lift a lighter weight for several reps to near failure, and a formula projects the single-rep max. Epley uses weight × (1 + reps ÷ 30); Brzycki uses weight × 36 ÷ (37 − reps). This calculator averages the standard formulas for a robust estimate.
How many reps give the most accurate estimate?
Roughly two to eight hard reps taken close to failure. In that range the formulas agree within a few percent. Above ten reps the estimate drifts, because a long set measures muscular endurance as much as maximal strength, and endurance varies widely between people.
What percentage of my max should I train at?
It depends on the goal. Above about 85% of your max builds maximal strength at low reps; 65–80% drives muscle growth at moderate reps; below 60% builds endurance and suits warm-ups and technique. The percentage table converts your estimated max into each of these loads.
Should I actually test my one-rep max?
Rarely, and never without a proper warm-up and a spotter for lifts like the bench press. A true max attempt is taxing and carries injury risk. The whole point of estimating is to know your max safely from a normal working set, so most lifters never need to test a genuine single.