One Rep Max Calculator: Estimate Your 1RM for Bench, Squat, and Deadlift
A one rep max calculator estimates the heaviest weight you could lift for a single clean repetition of a lift such as the bench press, squat, or deadlift, using a set you have already completed.
One Rep Max Calculator
What a One Rep Max Is and Why You Estimate It
Your one rep max, written as 1RM, is the most weight you can move for a single full repetition with sound technique. It is the reference point most strength programs are built around, because training loads are usually prescribed as a percentage of it. Rather than attempting a true maximal single, which is fatiguing and carries more risk, most lifters plug a recent submaximal set, such as 185 lb for 5 reps, into a prediction formula and program from that estimate.
The trade-off is accuracy. A predicted 1RM is a close approximation, not a guaranteed number, and it drifts further from reality the more reps you use to generate it. Fewer reps mean a tighter estimate.
How the One Rep Max Formulas Work
Four prediction formulas account for almost every 1RM calculator online. Each takes the weight lifted (w) and the reps completed (r) and returns an estimated single.
- Epley (1985): 1RM = w x (1 + r / 30)
- Brzycki (1993): 1RM = w x 36 / (37 – r)
- Lombardi (1989): 1RM = w x r ^ 0.10
- Lander (1985): 1RM = (100 x w) / (101.3 – 2.67123 x r)
Epley and Brzycki are the two most cited, and they agree exactly at 10 reps. Below ten reps, Epley returns the higher figure; above ten, Brzycki does. The calculator above lets you switch between all four so you can see the spread for your own numbers.
Here is the same submaximal set run through each formula, so you can see how far apart they land:
| Formula | Estimated 1RM from 185 lb x 5 reps |
|---|---|
| Epley | 216 lb |
| Brzycki | 208 lb |
| Lombardi | 217 lb |
| Lander | 210 lb |
The 9 lb spread between the lowest and highest estimate is typical at five reps and widens as reps climb, which is the single biggest reason to keep your test set short.
One Rep Max Training Percentage Chart
Once you have an estimated 1RM, every other training load is a percentage of it. The table below takes the Epley estimate from the example above (216 lb) and breaks it into the working percentages most programs use.
| % of 1RM | Load (lb) | Typical goal |
|---|---|---|
| 100% | 216 | Max strength / testing |
| 95% | 205 | Max strength |
| 90% | 194 | Strength |
| 85% | 183 | Strength / power |
| 80% | 173 | Hypertrophy |
| 75% | 162 | Hypertrophy |
| 70% | 151 | Hypertrophy / endurance |
| 65% | 140 | Endurance |
Change the lift, weight, reps, or formula in the calculator and this entire table rebuilds around your own estimate.
Reps to Percentage of 1RM Reference
If you would rather work backward from a rep target, the classic reps-to-percentage chart maps how many reps a given percentage of your max should allow. These values line up closely with the widely cited training-load chart from the National Strength and Conditioning Association (NSCA).
| Reps | % of 1RM | Training focus |
|---|---|---|
| 1 | 100% | Max strength / testing |
| 2 | 95% | Max strength |
| 3 | 93% | Strength |
| 4 | 90% | Strength |
| 5 | 87% | Strength |
| 6 | 85% | Strength / power |
| 8 | 80% | Hypertrophy |
| 10 | 75% | Hypertrophy |
| 12 | 70% | Hypertrophy / endurance |
| 15 | 65% | Endurance |
How Accurate Are 1RM Estimates
Every prediction formula assumes a tidy relationship between reps and load, and real lifters do not all fit that curve. Two people with an identical five rep max can have genuinely different true singles, because rep-out performance depends on muscle fiber makeup, training history, and how hard the set actually was.
A few patterns hold across the research:
- Low reps are far more reliable. Estimates are tightest at five reps or fewer and lose accuracy quickly past ten, where the formulas start to disagree by double digits.
- Epley tends to run high at high reps. For sets of eight to twelve, Epley recommends heavier loads than Brzycki, so a chart built on Epley can push a novice toward overreaching.
- The set has to be honest. A grindy, borderline-failure set predicts a very different max than a comfortable set at the same weight and reps. Feed in a set you took close to failure with clean form.
Treat the number as a planning tool, not a scoreboard. For programming, pick one formula and stay with it so your percentages move consistently from week to week.
Bench Press vs Squat vs Deadlift
A single general formula works for any barbell lift, which is why one calculator covers the bench press, squat, deadlift, and overhead press. That said, the lower-body lifts behave a little differently in practice. The squat and especially the deadlift tend to allow more reps at a given percentage than the bench press, so a generic formula can slightly underestimate a deadlift single built from a high-rep set. For that reason the NSCA publishes exercise-specific coefficients rather than one universal multiplier, and tools like the Omni one rep max calculator apply lift-specific factors. When precision matters on the deadlift, keep the test set to three to five reps.
Common Mistakes When Estimating Your Max
- Using a 15-rep set. High-rep estimates are the least trustworthy. Test with a heavy triple or five.
- Switching formulas between workouts. Different formulas give different numbers, so mixing them makes your week-to-week loads inconsistent.
- Chasing the estimate as if it were tested. Program off it, then let real sets confirm or adjust it.
- Forgetting to round to loadable plates. A calculator may say 183 lb; load the nearest 5 lb you can actually put on the bar.
For a second opinion on the math, the NASM one rep max resource and the ExRx one rep max reference both walk through the standard formulas.
FAQ
How do I calculate my one rep max? Take a set you recently completed, enter the weight and the number of clean reps into a formula like Epley, and read the estimated single. For 185 lb x 5 reps, Epley returns about 216 lb.
Which formula is more accurate, Epley or Brzycki? They agree exactly at ten reps. Below ten, Epley reads higher and Brzycki lower; above ten it reverses. For low-rep sets the two land within a few percent of each other, so either is fine as long as you stay consistent.
Should I actually test my true one rep max? Most lifters do not need to. A submaximal set of three to five reps run through a formula gives a close estimate without the fatigue and risk of a maximal single. Attempt a true max only when you are peaked and have a spotter.
If I bench 185 for 5 reps, what is my max? Roughly 208 to 217 lb depending on the formula, with the Epley estimate at about 216 lb.
Why do the formulas give different numbers? Each uses a different mathematical relationship between reps and load. Epley is linear, Brzycki is closer to an exponential curve, and Lander and Lombardi use their own coefficients, so they diverge most at higher rep counts.
References
- NASM — One Rep Max Calculator and formulas
- Omni Calculator — One-Rep Max and NSCA coefficients
- ExRx.net — Predicting One-Rep Max
