One-Rep Max Calculator
Estimate your one-rep max from a lighter set using the Epley and Brzycki formulas, plus a training percentage table.
| % of 1RM | Training weight |
|---|---|
| 95% | 205 lb |
| 90% | 194.2 lb |
| 85% | 183.4 lb |
| 80% | 172.6 lb |
| 75% | 161.9 lb |
| 70% | 151.1 lb |
| 65% | 140.3 lb |
These are estimates for planning training, not a reason to test a true 1-rep max alone or without safety bars. Beginners do not need to find a real max; train off the estimate instead.
How it works
A one-rep max (1RM) is the heaviest weight you could lift for a single clean rep. You rarely need to find that number by actually testing it. Instead, this calculator takes a set you already did (a weight and a rep count) and extrapolates what your max would be, using two formulas that were built from real lifting data: Epley and Brzycki. They agree closely at low reps and drift apart a bit as reps climb, which is why both are shown side by side instead of picking one as "correct."
Worked example: enter 185 lb for 5 reps. Epley scales the weight by a factor of 1 plus reps divided by 30, so 185 × (1 + 5/30) works out to 215.8 lb. Brzycki divides the weight by a shrinking fraction, 36 over (37 minus reps), which gives 185 × 36/32, or 208.1 lb. Both land in the same neighborhood, which is the point: neither number is a target to chase, they are a range to plan around. The percentage table below takes the Epley estimate and scales it down, so at 80% of a 215.8 lb estimate you get 172.6 lb, a sensible weight for a heavier set of 3 to 5 reps.
Both formulas were built on submaximal sets, meaning someone stopped a few reps short of failure, not sets taken to the limit. If you use a set you took to true failure, both formulas will overestimate your real max a little. That is fine for programming purposes; it is not fine if you plan to actually load the bar to the estimated number and attempt it.
FAQ
Why do Epley and Brzycki give different numbers?
They were derived from different data sets using different math. At low reps (1 to 3) the gap is small, usually under 2%. By 8 to 10 reps the gap widens because the formulas extrapolate further from the actual set you performed. Showing both gives you a sense of how much uncertainty is baked into any estimate at that rep range.
Why cap this at 12 reps?
Past roughly 10 reps you are training more like an endurance set than a strength set, and both formulas start producing numbers that do not match what people can actually lift. Twelve is a soft ceiling here; treat anything past 10 reps as a rough guess rather than a number to plan a program around.
Should a beginner test a real one-rep max?
Generally, no. A true max attempt loads a joint and a nervous system that has not built the technique or bracing skill to handle it safely, and it is easy to get hurt chasing a number. Never attempt a true max alone or without safety bars or a spotter. Beginners get just as much benefit from training off an estimate for months before a real max attempt even becomes useful.
How do I use the percentage table?
Programs are usually written as a percent of your 1RM: "3 sets of 5 at 80%," for example. Once you have an estimate, look up the percentage the program calls for and load the bar to that number, rounding to the nearest plate you can actually load. Retest your estimate every few weeks as your lifts improve.
For more on picking a starting weight and building it up over time, see how much weight a beginner should lift, sets and reps explained, and what progressive overload is and how to use it.