How One-Rep Max Formulas Work
Testing a true one-rep max is fatiguing and carries more injury risk than a normal training set. Prediction equations let you estimate your max from a set you were already doing, ideally a heavy set of 2 to 6 reps.
The Epley equation, from strength coach Boyd Epley, adds about 3.3% to the weight for every rep you complete:
The Brzycki equation (Matt Brzycki, 1993) uses a curve that rises faster as reps climb:
The two formulas agree exactly at 10 reps. Below that, Epley runs a few percent higher; above it, Brzycki climbs faster. This calculator averages them by default to split the difference, and treats a single rep as your 1RM. Both get less reliable past 10 reps, which is why reps are capped at 15.
How to Use This Working Weight Chart
Different percentage ranges suit different goals on compound lifts like the squat, bench press, deadlift, and overhead press:
- Hypertrophy (70%-80% 1RM): about 8-12 reps per set, leaving 1-3 reps in reserve (RIR).
- Strength (80%-90% 1RM): heavier sets of 3-5 reps.
- Peaking (90%+ 1RM): singles, doubles, and triples to get ready for a max attempt or a meet.
Every row is rounded to the nearest 5 lbs (2.5 kg), or 2.5 lbs (1 kg) if your gym has fractional plates, so you never have to do plate math on the gym floor.
Frequently Asked Questions
How accurate is an estimated 1RM calculator?
Estimates are most reliable from heavy sets of about 2-6 reps. Past 10 reps, muscular endurance and pacing play a bigger role, so the estimate drifts further from what you could actually lift for a single.
Should I test a true 1RM or use an estimate?
Unless you are preparing for a powerlifting meet, an estimated 1RM gives you everything you need for programming without the fatigue and injury risk of a true max attempt.
Why does the chart round my weights?
Raw percentages produce unloadable numbers like 231.4 lbs. The chart rounds to the nearest 5 lbs (2.5 kg) by default, or 2.5 lbs (1 kg) if your gym has fractional plates, so you can load the bar right away.
What is the difference between Epley and Brzycki formulas?
Epley adds a fixed amount for every rep, while Brzycki's curve gets steeper as reps climb. The two match exactly at 10 reps. Below 10, Epley gives a slightly higher estimate; above 10, Brzycki does.
This calculator and its content are for educational purposes only and are not medical advice. Check with a physician before starting an intense resistance training program.
