One rep max calculator
Estimate one-rep max with Epley and compare it with a Brzycki cross-check.
What this calculator covers
Use this calculator to estimate a one-rep max from a set you have already completed. It uses Epley as the headline estimate and keeps Brzycki alongside it so the extrapolation is easier to sanity-check.
Rep-based max formulas are strongest on shorter sets and become less stable as reps climb. Treat the result as a training estimate, not a guarantee of what should go on the bar that day.
Frequently asked questions
- Why does accuracy drop as rep count increases?
- At higher rep counts, muscular endurance becomes a larger factor alongside raw strength. The formulas assume a relatively constant relationship between a multi-rep set and the one-rep maximum, but that relationship weakens as the set gets longer, making the extrapolation less reliable above about 5 to 6 reps.
- What is the difference between the Epley and Brzycki estimates?
- Both formulas extrapolate a one-rep max from a submaximal set, but they use different mathematical models. The Epley formula tends to produce slightly higher estimates, while Brzycki tends to be more conservative. Seeing both together helps identify when the two methods agree or diverge.
- Can I use this to program my training percentages?
- Yes — once you have an estimated one-rep max, you can calculate target loads as a percentage of that number. For example, 75 percent of a 200 lb max gives a working weight of 150 lb. Just remember the max is an estimate, so build in some margin when loading the bar.
- Should I attempt a true one-rep max to verify the estimate?
- Maximal attempts carry injury risk and require proper warm-up, spotting, and technique. Many coaches prefer to use submaximal tests and formula estimates rather than true one-rep max attempts, especially outside of competition. The estimate here is meant to inform training loads, not to prompt an immediate max attempt.
Tool
Run the calculation
Result
RESULT · 1RM
â„–145
Primary result
233.3 lb
Lifting 200.0 lb for 5 reps gives an estimated one-rep max of 233.3 lb with the Epley formula, while Brzycki cross-checks at 225.0 lb.
- Weight lifted
- 200.0 lb
- Reps completed
- 5
- Epley estimate
- 233.3 lb
- Brzycki cross-check
- 225.0 lb
Step-by-step solution
- 1.Apply the Epley default: 200.0 x (1 + 5/30).
- 2.Cross-check with Brzycki: 200.0 x 36 / (37 - 5).
- 3.Use the Epley estimate as the primary display and compare it with the Brzycki value for sanity-checking short rep sets.
Walkthrough
Visual walkthrough
One-rep-max formulas treat a multi-rep set as a proxy for your true top-end lift, then extrapolate back to a single repetition.
01
Start from the completed set
200.0 lb x 5
The observed training set is the only direct input; the one-rep max is inferred from it.
02
Run the Epley and Brzycki formulas
Epley and Brzycki
Both formulas are most defensible on short sets, which is why the calculator caps reps at 15.
03
Use the Epley estimate as the headline
The Brzycki result stays visible as a cross-check instead of replacing the default estimate.
233.3 lb