Free tool
1 Rep Max Calculator: Epley Formula & Max PR Estimator
Work out your max PR from any clean set. The calculator runs the Epley formula alongside Brzycki and Lombardi, so you can see how much the three estimates disagree before you trust a number. The chart below turns that estimated 1RM into working loads for every common rep range, so you can program training days directly from your workout log.
Estimated 1 rep max
260 lbs
Epley 263 · Brzycki 253 · Lombardi 264
Percentage load chart
| Reps | % of 1RM | Load |
|---|---|---|
| 1 | 100% | 260 lbs |
| 2 | 95% | 247 lbs |
| 3 | 93% | 242 lbs |
| 4 | 90% | 234 lbs |
| 5 | 87% | 226 lbs |
| 6 | 85% | 221 lbs |
| 8 | 80% | 208 lbs |
| 10 | 75% | 195 lbs |
| 12 | 70% | 182 lbs |
| 15 | 65% | 169 lbs |
How the Epley Formula Works
The Epley formula is one line of arithmetic:
1RM = weight × (1 + reps ÷ 30)
It was developed by Boyd Epley, a strength and conditioning coach at the University of Nebraska, and it has been the gym default ever since. Divide the reps by 30, add one, multiply by the weight you can lift, and you have your estimated 1RM.
A worked example: five reps at 225 lb on the bench press gives 225 × (1 + 5 ÷ 30) = 262.5 lb. That is the load you would be predicted to lift for a single repetition on a good day.
Epley vs Brzycki vs Lombardi
All three are curve fits over the same relationship between load and reps, and they disagree most at the edges. Brzycki divides by a shrinking denominator, so it reads conservative below five reps. Epley scales linearly with reps, so it reads higher on high reps. Lombardi uses a power curve and sits between the two on most inputs.
Inside a rep range of three to six they land within a few percent of each other. That agreement is the real signal: when the three estimates cluster, the number is usable. When they spread out, your set was too long to extrapolate from.
Turning an Estimate Into Working Sets
A one rep max is only useful if it sets your training loads. The percentage chart above converts your estimated 1RM weight into the loads you actually put on the bar. Hypertrophy work mostly lives between 65% and 80%. Strength work sits between 80% and 92%. Anything above 95% is a test, not training.
Program from the estimate rather than from a true max you tested months ago. Recalculate from your workout log every four to six weeks. If the number is drifting up, your working sets should drift up with it.
When You Should Not Use a Rep Max Calculator
Skip the estimate if the set was grindy, if your form broke down, or if it was a higher rep set past ten. All three formulas assume a clean set taken close to failure. Feed them a sloppy set and you calculate a 1RM you cannot lift, then program every session off a number that is wrong.
Frequently Asked Questions
What's the most accurate 1RM formula?
No formula is universally most accurate — they're all extrapolations from sub-maximal sets. For 2-10 reps they agree within a few percent. Brzycki trends slightly conservative below 5 reps, Epley trends slightly higher above 8 reps. Averaging all three usually gives a reliable estimate for programming.
How many reps should I use for the best estimate?
3-6 reps is the sweet spot. Under 3 reps doesn't give the formulas enough data points; above 10, the estimate gets less reliable because rep endurance varies more between people. A clean 5-rep set with 0-1 reps in reserve is ideal.
Should I test a true 1RM?
Only if you're competing in powerlifting or have a clear reason. True 1RM attempts are high-risk (form breakdown, bar speed collapse, peaking fatigue) and most training protocols use estimated or working 1RMs just fine. Program off 85-90% of your calculated 1RM for the big lifts and leave true maxes for meets.
How does Level use your 1RMs?
Level tracks your working max on each major lift and uses it to prescribe session-specific loads (e.g. '4×6 at RPE 7 ≈ 82% of current 1RM'). As you log sets with higher reps-in-reserve, Level increases your working max and the programmed loads adjust automatically.
What is the Epley formula?
The Epley formula estimates a one rep max as weight × (1 + reps ÷ 30). Developed by Boyd Epley, a strength and conditioning coach at the University of Nebraska, it is the most widely used 1RM estimate in the gym. Because reps are divided by 30, the estimate climbs steadily as rep count rises, which is why Epley reads slightly high on high reps.
Is the Epley formula accurate for high reps?
It is most reliable under about 10 reps. Past that, rep endurance varies too much between people for any single repetition estimate to hold. Two lifters with the same true max can differ by several reps at 70% load. Use a heavier set in a low rep range when accuracy matters.
How do I find my max PR without testing it?
Take the heaviest clean set in your workout log, enter the weight you can lift and the reps you completed, and read the estimate. That number is your max PR for programming purposes. Re-check it every few weeks rather than after a single good session.
What should I do with the percentage chart?
Use it to pick loads for your working sets. Most hypertrophy work sits between 65% and 80% of 1RM, strength work between 80% and 92%. Program from the estimate, not from a true max you tested months ago.