Max Lift Estimator
Estimate your one-rep max and explore rep curves
Have you ever been in the gym watching someone lift and wondered: "Could I lift that same weight?" Or sometimes you're just not sure how to scale the reps when you increase the weight.
I was wondering, are there formulas for this stuff?
Turns out there are—many of them. And they each work better for different situations, which is where things get interesting.
The four types and when to use them
Researchers have developed several formulas over the decades, each with its own strengths:
Epley (1985): 1RM = W × (1 + R/30)
Linear and simple. Best for 3–10 reps in general gym use. If you bench 100kg for 8 reps, this predicts about 127kg max.
Brzycki (1993): 1RM = W / (1.0278 – 0.0278×R)
Hyperbolic curve, popular in collegiate testing. Best for 2–10 reps, especially lower rep ranges. Same example gives about 125kg.
Lombardi (1989): 1RM = W × R0.10
Power law that works better for higher reps (10–20+). Great for bodybuilding-style sets and endurance athletes.
O'Conner (1989): 1RM = W × (1 + 0.025×R)
Similar to Epley but more conservative. Good for 3–12 reps when you want to err on the cautious side.
Why they all give different answers
Here's the thing: these are all approximations based on averages. Your actual performance depends on a bunch of factors that make this more art than science.
Exercise type matters hugely. At 70% of your max, you might bang out 19 reps on leg press but only 14 on bench press. Big compound movements, especially lower body, let you grind out way more reps than small isolation exercises.
Your training background shapes everything. Endurance athletes can do 20 reps at 80% of their max while equally strong powerlifters might only manage 12. Fast-twitch dominant lifters excel at heavy singles but fade quickly at higher reps.
Tempo and mindset aren't trivial. Fast reps can yield 12 reps at 65% while slow controlled reps drop you to 7 at the same weight. Mental factors—fear, discomfort, willingness to push to true failure—can easily swing results by several reps.
Take it all with a grain of salt
These formulas give you a ballpark, not gospel truth. Your muscle fiber composition, whether you're doing major lifts or minor ones, how you've been training, and even psychological factors all influence the numbers.
The variability gets wild at the extremes—very low reps (1-3) and very high reps (20+)—so treat any predictions there as rough estimates at best.
But I thought it was fun to explore, and it gives you a starting point for programming training loads. Use multiple formulas, track your own patterns over time, and adjust based on what you actually experience in the gym.
Ready to explore your numbers?
Head over to the App to plug in your current lifts and see what the different formulas predict, or use the Chat if you want to ask questions about how these formulas work or when to use each one.