Seven formulas, one consensus
Epley, Brzycki, Lander, Lombardi, O’Conner, Mayhew and Wathen all run at once. You see the spread and the average, so you know how much confidence the estimate deserves.
Strength Tool
One Rep Max Calculator
Enter the weight you lifted and how many clean reps you got. This one rep max calculator runs seven validated 1RM formulas at once, then gives you a full percentage chart, rep-max table, warm-up plan and barbell plate loading — in kg or lb.
- ✓ 7 formulas averaged
- ✓ kg & lb supported
- ✓ Plate loading included
- ✓ No sign-up, instant results
Calculate your 1RM
kg
Total bar weight, including the bar itself.
reps
Clean reps with good form. Accuracy is best at 1–10.
Used for rounding and warm-up guidance.
Estimated one rep max
0kg
Working weight (80%)
0
Typical hypertrophy load for sets of 8.
Strength load (90%)
0
Heavy singles and doubles territory.
| % of 1RM | Load | Approx. reps | Training focus |
|---|
| Rep max | Estimated load | % of 1RM | Best used for |
|---|
| Formula | Estimated 1RM | Difference | Known for |
|---|
The headline number above is the mean of all seven equations, which reduces the bias any single formula carries at higher rep ranges.
| Set | Load | Reps | Rest |
|---|
Plate loading per side
Why this 1RM calculator is more accurate
Most max rep calculators run a single equation and print one number. That number can be off by 10–15% at higher rep ranges, because each formula was validated on a different population and a different lift.
Full percentage chart
Every load from 50% to 100% of your one rep max, with realistic rep targets and the training goal each zone serves — not just a bare number you still have to work with.
Barbell plate loading
The only 1RM calculator that tells you exactly which plates to put on each side of the bar for your top set, in kg or lb, with the bar weight already subtracted.
Warm-up ramp included
A five-set ramp scaled to your estimated max, so you arrive at your working weight primed rather than pre-fatigued.
Sensible rounding
Results snap to 2.5 kg or 5 lb increments, because those are the plates that actually exist in your gym. No 87.3 kg targets you cannot load.
Instant and private
Everything runs in your browser. No account, no email, no data leaving your device, and no waiting on a page reload between calculations.
How to use the one rep max calculator
You need one honest set. The estimate is only as good as the effort behind the reps you enter.
- Pick a recent hard setUse a set you took close to failure — roughly one or two reps left in the tank. A comfortable set will under-estimate your max badly.
- Enter the total bar weightInclude the barbell itself: 20 kg or 45 lb for a standard Olympic bar. Switch units at the top right at any time and the numbers convert instantly.
- Enter the reps you completedCount only clean reps. Grinding, bouncing or losing position mid-rep inflates the input and the estimate along with it.
- Read the range, not just the numberThe headline figure is the average. The range underneath shows how far the individual formulas disagree — a wide spread means treat the number cautiously.
- Programme from the percentage chartTake your target percentage for the day and use the load column. That is your working weight for that session.
- Retest every four to eight weeksRecalculate after a training block rather than every session. See our guide to deload weeks for timing a retest properly.
The 1RM formulas explained
Every one rep max equation is a curve fitted to real lifters. They agree closely at low reps and diverge as reps climb, which is exactly why averaging them helps.
Epley and Brzycki
Epley — 1RM = w × (1 + r / 30) — is the most widely used. It is linear and slightly generous above eight reps.
Brzycki — 1RM = w × 36 / (37 − r) — is more conservative in that same range. The two are identical at 10 reps and drift apart either side of it, which makes them a useful pair.
Lander, Lombardi and O’Conner
Lander uses a linear denominator very close to Brzycki. Lombardi is the only exponential model in common use — 1RM = w × r^0.10 — and holds up better at high rep counts.
O’Conner is the simplest of all, adding 2.5% per rep. It is easy to do in your head at the rack and surprisingly close for sets of three to six.
Mayhew and Wathen
Both were derived from bench press testing on trained athletes and use exponential decay terms. They tend to sit slightly higher than Brzycki on upper-body lifts.
If you only train the bench press, these two carry more weight than the general-purpose equations.
Which one should you trust?
No single one. Research consistently shows prediction error grows with rep count — estimates from sets of one to five are reliable within a few percent, while sets of 12 or more can be off by 10% or worse.
That is why this calculator reports the mean of all seven and shows you the spread. When the formulas cluster tightly, your estimate is solid. When they scatter, test with fewer reps.
Why knowing your one rep max matters
Percentage-based programming — 5/3/1, Texas Method, conjugate, most powerlifting peaking blocks — is built entirely on an accurate 1RM.
- You stop guessing your working weights. A percentage chart turns “that felt heavy” into a repeatable prescription.
- You avoid testing a true max. A genuine one rep max attempt is fatiguing and carries real injury risk. A calculated estimate gets you most of the information for none of the cost.
- You can track progress objectively. An estimated max climbing across blocks is clear evidence your programme works, even when your test-day numbers fluctuate.
- You can compare across lifts. Ratios between squat, bench and deadlift maxes reveal weak points long before they stall your total.
- You train in the right zone. Strength, hypertrophy and endurance adaptations sit in different percentage bands. Without a max you cannot target any of them deliberately.
Get the most from your estimate
Pair your max with the rest of your training picture. Progressive overload only works if recovery and nutrition keep up — use the macro calculator to set protein and calorie targets, and the body fat calculator to see whether added weight is muscle or not.
New to the barbell? Start with our guide on strength training for beginners before chasing heavy singles, and read why grip strength is worth training on its own.
One rep max calculator FAQs
The questions lifters ask most about estimating a max safely.
Very accurate from low-rep sets and progressively less so as reps climb. Estimates built on sets of one to five typically land within 2–5% of a tested max. Sets of ten or more can drift 10% or further, because rep endurance varies far more between people than maximal strength does. Averaging seven formulas, as this calculator does, narrows that error compared with using any single equation.
Three to six reps is the sweet spot. That range is heavy enough to reflect true maximal strength but light enough to perform safely without a spotter setup or a full peaking phase. Below three reps you are effectively testing a max anyway; above eight, muscular endurance starts dominating the result.
No. You need to calculate it separately for each lift. Rep performance also differs by movement: most people manage more reps at a given percentage on the squat and deadlift than on the bench press or overhead press, because larger muscle groups and shorter ranges of stability tolerate volume differently. Calculate each lift from its own test set.
Only if you compete, and only after a dedicated peaking block with experienced spotters and safety pins. For everyone else the risk-to-benefit ratio is poor: a true max attempt is technically demanding, fatiguing for days, and offers little information a calculated estimate does not already give you.
Every four to eight weeks, at the end of a training block rather than mid-block. Recalculating too often chases day-to-day noise from sleep, stress and nutrition rather than genuine strength change. A rep-out set in the final week of a block, taken when you are relatively fresh, gives the cleanest input.
It depends on the adaptation you want. Maximal strength work sits at 85–95% for one to five reps. Hypertrophy is best served by 67–80% for six to twelve reps. Muscular endurance sits below 67% for higher reps. Most well-built programmes rotate through all three bands across a training year rather than living in one.
The formulas themselves do not use bodyweight, but training experience affects how well they fit you. Well-trained lifters usually complete fewer reps at a given percentage than novices, because they can recruit closer to their true maximum in a single effort. If you are experienced and the estimate consistently reads high, favour the more conservative Brzycki and Lander figures in the formula breakdown.
Yes for the estimate itself — the equations do not care what the load is attached to. Select “Other lift” so results are not rounded to barbell plate increments, and ignore the plate loading panel. For dumbbell work, enter the combined weight of both dumbbells if you are pressing with two.
Stop guessing your working weights
One honest set is all it takes. Run the numbers, take the percentage chart into your next session, and let your programme do the rest.
This one rep max calculator provides estimates for training guidance only. It is not medical advice. Warm up thoroughly, use safety pins or a spotter for heavy work, and speak to a qualified coach or clinician before attempting maximal loads if you have an injury history.