1RM calculator
Updated on 18 September 2026
Your 1RM is the heaviest load you can lift once on an exercise. It is estimated from a submaximal set — most reliable between 1 and 6 reps — using the Epley and Brzycki formulas, without testing a true max.
Your 1RM (one-rep max) is the heaviest load you can lift once on an exercise. It is the reference for calibrating your sessions: most programs express their loads as a percentage of 1RM. Rather than testing a true max — tiring and risky — this tool estimates it from a submaximal set.
Enter a weight and a rep count between 1 and 12 (the estimate loses accuracy beyond that).
How the calculation works
The tool combines two proven formulas, Epley's and Brzycki's, and averages them to smooth out their differences. From the weight lifted and the reps performed, it projects the load you could lift just once.
The estimate is most reliable between 1 and 6 reps. Beyond 10-12 reps, endurance and technique take over from pure strength, and the projection becomes approximate: treat the result as a ballpark then.
What the 1RM is for
Knowing your 1RM lets you pick the right load for your goal: around 85-95% for strength, 70-80% for hypertrophy, below 70% for endurance. The load table above gives you these markers directly.
It is also an excellent progress indicator: if your estimated 1RM climbs month after month, you are simply getting stronger. Log your performances to track this curve over time.
Turning your 1RM into working loads
The main use of your 1RM is to set your working loads as percentages. Once your max is estimated, the load table gives you the weight for each zone directly: around 90% for strength on 3-4 reps, 75-80% for hypertrophy on 8-12 reps, and 65% or less for volume and technique.
These percentages are not rigid: your daily form, sleep and recovery change what you can actually lift. Adjust by feel, and recompute your 1RM every few weeks so your loads track your progress.
Mistakes that skew the estimate
Technique is the first invisible source of cheating: a partial rep, a bounce off the bar or help from the upper body let you lift more, but the resulting estimate no longer reflects your true strength. Film yourself from the side occasionally to check your range of motion stays the same from session to session.
Accumulated fatigue also skews the calculation: testing your reference set at the end of a session, after several heavy exercises, gives a lower figure than your real capacity. For a reliable result, perform your test set early in the session, after a full warm-up but before fatigue sets in.
Relative 1RM and comparing between lifters
Comparing raw 1RMs between two people does not mean much if their body weights differ: instead you use the relative 1RM, meaning the 1RM divided by body weight. A 70 kg lifter who benches 140 kg has a ratio of 2, a marker of advanced strength.
This ratio also lets you track progress independently of weight changes: if you gain 2 kg of muscle and your absolute 1RM stalls, your relative 1RM actually drops slightly. Keep an eye on both figures rather than just one.
The 1RM in a strength program
Structured strength programs (5/3/1, Starting Strength, Texas Method) build their entire cycle around a training 1RM, often set slightly below the real 1RM as a safety margin. This figure is the base for weeks of progressive loading, before a test or a new estimate.
Without a reference 1RM, it is hard to know whether you are really progressing or just stalling while changing loads at random. This is why most serious programs require knowing this figure, at least roughly, before starting a cycle.
Frequently asked questions
Is the estimate accurate?expand_more
It is very reliable on short sets (1 to 6 reps), within a few percent. The more reps, the greater the uncertainty. Use it as a guide, not an absolute truth, and refine it with experience.
Should I test my true 1RM in the gym?expand_more
It is not necessary to progress, and it is discouraged for beginners: a true max demands perfect technique and a spotter. Estimating from a set of 3 to 5 reps is far safer day to day.
How often should I recompute my 1RM?expand_more
Every 4 to 6 weeks is enough for most trainees: that is how long it takes for strength to change measurably. Recompute from a solid recent set rather than attempting a true max.
Is the 1RM the same on every exercise?expand_more
No, it is specific to each lift: your deadlift 1RM will be far higher than your bench press. Estimate it lift by lift, on the movements where you track your progress.
Epley or Brzycki: which formula is more reliable?expand_more
Both are very close on short sets, which is why the tool averages them. Brzycki tends to give a slightly lower figure beyond 10 reps; on 1 to 5 reps the difference is negligible.
Can I estimate my 1RM without a machine or barbell?expand_more
Yes, the formula works with any measurable external load: dumbbells, kettlebells, or even a weighted vest. It is less relevant for bodyweight exercises, though, where the max rep count is a better indicator than load.
What if my estimated 1RM stalls for several months?expand_more
A prolonged plateau often comes from a lack of variation in training, insufficient recovery, or calories that are too low. Change your rep range for a few weeks, check your sleep, and make sure you eat enough protein and calories to progress.
Is the estimated 1RM reliable for women?expand_more
Yes, the Epley and Brzycki formulas have been validated on mixed populations and do not depend on sex: they only relate the weight lifted to the number of reps. Reliability depends on the rep range, not the person's sex.
Do I need a spotter to use this tool?expand_more
No, that is precisely the point: you perform a safe, submaximal set, alone or with company. A spotter is still recommended for safety on heavy lifts like the bench press, but is not required for the estimate itself.
What is the difference between 1RM and your usual working load?expand_more
Your usual working load is the one you use for multi-rep sets, typically 60 to 85% of your 1RM. The 1RM itself is almost never used in training: it serves as a reference to calculate those loads, not as a daily working weight.
Does the 1RM change depending on the warm-up?expand_more
An insufficient warm-up reduces your real performance and underestimates your 1RM; an excessive warm-up tires you before the test set and has the same effect. A progressive warm-up of 3 to 4 steps, without going to failure, gives the most reliable measurement.
Can you estimate a 1RM for isolation exercises?expand_more
Technically yes, but it is not very useful: isolation exercises (curl, extension) are almost never trained as a percentage of 1RM. Save this calculation for compound lifts (squat, bench press, deadlift, overhead press) where percentages actually make sense.
Does the tool work for beginners?expand_more
Yes, but carefully: beginners progress fast from session to session, so the estimate becomes outdated more quickly than for an experienced lifter. Recalculate more often early on, every 2 to 3 weeks for example.
Is 1RM useful for sports other than strength training?expand_more
Yes: powerlifting, strongman, and even some team sports use it to calibrate physical preparation. As soon as a strength lift structures training, knowing your 1RM helps program loads intelligently.
Sources
- menu_bookEpley formula
- menu_bookBrzycki formula
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