1RM Calculator: Estimate Your One-Rep Max

How to use the 1RM calculator

1. Choose kilograms or pounds.
2. Enter the weight lifted and the number of reps you completed.
3. Pick the Brzycki formula, the Epley formula or the Lombardi formula. Brzycki is the default.
4. Read your estimated 1RM (e1RM), then the two tables under it: your estimated rep max for every rep count from 1 to 12, and the training weight at each percentage of your 1RM. Everything updates as you type.

Feed the 1RM calculator one hard submaximal set of 1 to 12 repetitions (reps) finished with proper form. The result is an estimate rather than a tested maximum, so plan around a margin of error of roughly 5 to 10 percent.

What a one rep max (1RM) is

A one rep max (1RM) is the heaviest weight you can lift for a single repetition on a given exercise, through a full range of motion and with technique you would still count. It is the usual shorthand for maximal strength, and it is the number powerlifting is scored on.

A 1RM calculator works backwards from a set you already did: the more reps you completed at a weight, the further that weight sits below your single. Nothing here is measured. The equations were fitted to group data, so they describe what a typical lifter's maximal strength looks like given that set, not what yours is. That is enough for picking training weights and tracking change over time, and not enough to write on a competition attempt card.

Brzycki, Epley and Lombardi formulas compared

The calculator applies the formula you select and rounds the result to 0.1 kg / 0.1 lb. A single you enter counts as your 1RM under every formula.

• Brzycki formula: 1RM = weight / (1.0278 - 0.0278 x reps)
• Epley formula: 1RM = weight x (1 + reps / 30)
• Lombardi formula: 1RM = weight x reps^0.10

All three take the same two inputs and disagree, because each one draws a different curve through the relationship between weight lifted and reps. The gap between them is the honest width of the estimate.

The Brzycki formula is the default and returns the lowest of the three up to about 7 reps, which is the conservative choice if you plan to load the result. The Epley formula is the most widely quoted and rises in a straight line with reps. The Lombardi formula is the most aggressive on short sets and the most conservative on long ones.

Expect the formulas to disagree with your tested max too, because rep endurance varies between people and between exercises. Two lifters with the same tested single can be several reps apart at 80 percent. That is a property of the lifter rather than an error in the calculator, and it is the reason to compare your estimate with your own previous estimate instead of anyone else's. Which formula is "right" matters less than picking one and keeping it: a change in the estimate only means something if the formula, the exercise, the rep range and your technique all stayed the same.

One rep max chart: rep maxes from 1 to 12 reps

A rep max is the most weight you can lift for a given number of reps, so your 5-rep max (5RM) is the heaviest weight you can manage for 5. The chart gives each rep max as a percentage of your one rep max under all three formulas. It is the same arithmetic as the rep max table in the calculator, written out so you can use it without one.

To turn the chart into weights, multiply your 1RM by the percentage. Say you bench pressed 100 kg / 225 lb for 5. The Brzycki formula puts your 1RM at 112.5 kg / 253.2 lb, which makes your 3-rep max about 106 kg / 239 lb and your 8-rep max about 91 kg / 204 lb. That is all a max rep calculator does: the formula that estimates a single from a set also runs backwards from the single to any other rep count.

Compare the columns before you trust one. The three formulas stay within about 3 percentage points of each other from 6 to 8 reps and drift apart at both ends. At 2 reps the Brzycki formula expects 97 percent of your max where the other two expect about 93, and at 12 reps the Lombardi formula expects 78 percent where the Brzycki formula expects 69. A rep max far from the set you entered carries the most error, so a 3-rep max worked out from a set of 10 is a rough guide at best.

Percentages of 1RM chart

Percentages turn the estimate into training weights. The calculator prints the full 50 to 100 percent range for your own number; the chart below shows what each percentage is normally used for, worked out from the 112.5 kg / 253.2 lb bench press estimate above.

The one rep max chart above answers the reverse question of how many reps a percentage allows: 80 percent of your 1RM is about an 8-rep max under the Brzycki formula. Below about 70 percent every formula passes 12 reps, where the estimates stop being reliable.

The 2026 ACSM position stand reports that voluntary strength was enhanced by loads at or above 80 percent of one-repetition maximum performed through a complete range of motion, which is the practical reason to know roughly where your working sets sit. A percentage still says nothing about how hard a set felt on the day, so pair it with RPE (Rate of Perceived Exertion): training intensity: RPE, RIR and percentage of 1RM covers how the two fit together.

Using the 1RM calculator for bench press, squat and deadlift

The formulas are the same for every lift. What changes is which set to enter and how far to trust the answer. Percentage-based training assumes multi-joint barbell lifts, and so do these equations: they work best on the bench press, the squat variations, the deadlift variations and the overhead press, where a set ends because the muscles involved ran out of force rather than because one small link gave up first.

Bench press 1RM

The bench press is the easiest lift to estimate from, because a bench set usually ends when the bar stops moving rather than when your position falls apart. Read the estimate from 3 to 6 reps, and set safeties or use a spotter for the set you enter. A bench press of 100 kg / 225 lb for 5 gives an estimated 1RM of 112.5 kg / 253.2 lb with the Brzycki formula, 116.7 kg / 262.5 lb with Epley and 117.5 kg / 264.3 lb with Lombardi. Keep the grip width and the pause, touch-and-go or paused on the chest, the same every time you re-estimate, because either one changes how much you can lift.

Squat 1RM

Depth is what ruins squat estimates: reps cut five centimeters / two inches short are a different exercise. Read from 3 to 5 reps, film the set if you are unsure, and enter only the reps you would count. A back squat of 140 kg / 315 lb for 3 gives an estimated 1RM of 148.2 kg / 333.5 lb with the Brzycki formula. Estimate the front squat separately, since it usually fails at the trunk rather than the legs.

Deadlift 1RM

The conventional deadlift, the sumo deadlift and the trap bar deadlift have different leverages and deserve separate estimates. Keep the grip the same each time, reset the bar between reps, and stay at 3 to 5 pulls. At deadlift weights the gap between formulas gets expensive: 180 kg / 405 lb for 4 gives 196.4 kg / 441.9 lb with the Brzycki formula and 206.8 kg / 465.2 lb with Lombardi, and that 10 kg / 23 lb is the difference between a heavy single and a rep you do not finish. Plan heavy pulls from the lower number. A Romanian deadlift (RDL) is not a max lift, so do not estimate a 1RM from one.

Overhead press and other lifts

Small muscles fatigue quickly in the overhead press, so the estimate holds only if you press the same way each time, strict or with leg drive, never a mix. For isolation and machine work the arithmetic is identical and the answer travels much less well. A dumbbell bench press estimate tells you nothing about your barbell bench press, and a weight-stack number belongs to one machine's leverage. For dumbbells, note whether you entered the weight per hand or the pair. Sets that run into muscular endurance territory, past 12 to 15 reps, fall outside what the equations model at all.

Strength standards: is your 1RM any good?

Strength standards express a 1RM as a bodyweight ratio (x bodyweight) so lifters of different sizes can be compared. Sites such as Strength Level publish them from large sets of submitted lifts, split by sex, bodyweight and age. The rounded benchmarks below are the ones in common use for adult men in powerlifting and general strength training, and they are an orientation aid rather than a measurement.

Standards for women run lower across all three lifts, and every set of standards shifts with age and bodyweight, so look up a figure matched to you rather than using these as a verdict. They are also worth less than your own trend line. A lifter moving from 1.2x to 1.4x bodyweight on the back squat is training well regardless of which label that lands in.

Test with a submaximal set, not a true max

For most lifters a submaximal set of 1 to 12 reps is the better test. A true max attempt costs recovery, needs a spotter or safeties on the bench press and back squat, and raises injury risk exactly when proper form is most likely to slip. The estimate from a clean set of 3 to 5 costs you nothing extra and is repeatable.

If you do test, ramp up in singles with progressively longer rests and stop the moment technique changes, not when the bar stalls. Beginners get least from testing: technique changes from week to week, so a maximal single mostly measures how well the lift held together that day. A set of 5 to 8 with 1 or 2 reps in reserve is more informative.

You do not need a tested number to program either. NASM prescribes intensity in its OPT Model as a percentage of 1RM for each phase, and both NASM and Barbell Medicine publish 1RM calculators of their own, because an estimate is precise enough to choose training weights from. If you have an injury, a medical condition or any pain during the lift, get advice from a qualified professional before loading a heavy single.

How to improve your one-rep max

Maximal strength responds to progressive overload driven by heavy work: sets of 1 to 5 reps at or above 80 percent of your 1RM, with enough easier volume around them that you can repeat the sessions. Keep the same exercises long enough to measure, add weight or reps when the previous session went well, and re-estimate at the end of a training block of 8 to 12 weeks rather than chasing the number weekly. The free 12-week powerlifting program lays out one such block in percentages of your 1RM. How to track progressive overload covers how to read the trend, and how to track personal records covers which kinds of PR actually show that training is working.

Estimated 1RM and total volume, over any range including your whole history. Both charts are free.

Which GymEvo calculator answers your question

Three of GymEvo's calculators run the same relationship between weight lifted and reps in different directions, and a fourth turns the answer into plates.

Plan the sessions after this one with the progressive overload calculator, or build a whole program around the exercises and days you have with the workout plan generator.

An estimate you work out once also decays: every set you log changes it. GymEvo stores weight, reps and an RPE value on every set, shows the previous session's numbers on the set you are about to perform, and keeps an estimated one-rep max across your whole training history, so the calculation above happens on its own as you train. The personal records tab also keeps rep records, your best set and estimated weight at each rep count, which is the one rep max chart above built from your own sets. The estimated 1RM chart is free; the full rep-record table and the remaining progress charts are Premium.

Targets appear per set, next to what you did last time.

The PRs tab. Records per metric are free; the full rep-record table below them is part of Premium.

Assumptions and limitations

• Rep-based formulas estimate rather than test a one rep max (1RM), and the three here disagree with each other about the same set.
• The estimate varies with the exercise, technique, range of motion, fatigue and how close the set was to failure.
• Accuracy drops as the rep count rises, so the calculator accepts no more than 12 reps.
• Rep maxes are the same formulas read in reverse, so they carry the same error, and they are least reliable far from the rep count you entered.
• The equations assume the set ended close to failure. A set with four reps left in reserve understates your max by about 11 percentage points, since each rep is worth roughly 2.8 points on the Brzycki curve. Training to failure covers how close is close enough.
• Do not attempt a maximal lift only because a calculator produced a number. If a lift hurts, or an injury or medical condition could change the answer, ask a qualified professional rather than a calculator.

Frequently asked questions

How accurate is a 1RM calculator?

Accurate enough to program from when you enter a hard set of about 5 reps, and less so as the reps climb. In a study of 70 men and women aged 18 to 69, a 5-rep max predicted bench press and leg press 1RM more accurately than a 10- or 20-rep max did. The authors' own bench press equation from 5-rep maxes had a standard error of about 3 kg / 7 lb, and they advised using no more than 10 reps in linear prediction equations. That equation lands within 2 percent of the Brzycki formula for 5-rep maxes between 60 and 140 kg / 135 and 315 lb. So enter a set of about 3 to 6 reps where you can, and treat an estimate from 10 to 12 reps as a rough guide.

What is the difference between a 1RM calculator and a max rep calculator?

People searching for a max rep calculator usually want one of two things: their one rep max from a set, or the weight they can manage for a given number of reps. Both come from the same formula run in opposite directions. A 1RM calculator takes a set you did, such as 100 kg / 225 lb for 5, and estimates your single. A rep max calculation starts from that single and gives the weight for another rep count, such as your 8-rep max. The calculator on this page does both, and the one rep max chart above gives the same relationship as percentages.

Why is my calculated 1RM higher than what I can actually lift?

Usually because of the set you entered or how you tested. A set of 8 to 12 reps leans on rep endurance, and a lifter with good endurance on that lift gets an estimate their single cannot match. A true single also takes practice: if you rarely lift above 90 percent of your max, a first real attempt can come in under the estimate. Re-estimate from a set of 3 to 5 before you load a heavy single, and use the Brzycki result, which is the lowest of the three formulas up to 7 reps.