Calculate your one rep max using the Epley formula. Enter the weight lifted and reps completed to estimate your 1RM for any exercise.
The Epley formula is the most widely used equation for estimating a one rep max (1RM) from sub-maximal effort. Published by Boyd Epley in 1985 while working at the University of Nebraska, it remains popular because of its simplicity and reasonable accuracy across moderate rep ranges (2–10 reps).
Knowing your 1RM is essential for percentage-based training programs. Instead of testing a true max — which carries injury risk and requires peak preparation — you can estimate it from a set of lighter reps. The Epley formula is especially accurate in the 3–7 rep range and tends to slightly overestimate at very high reps (15+).
This calculator applies the Epley formula, generates a percentage chart from 50–100% of your estimated 1RM, and shows the corresponding weight for each training percentage. Whether you are a beginner or experienced professional, this free online tool provides instant, reliable results without manual computation. By automating the calculation, you save time and reduce the risk of costly errors in your planning and decision-making process.
Testing a true 1RM requires careful setup and carries injury risk. The Epley formula lets you estimate your max from any set of 2–10 reps, making it practical for everyday training planning without the risk of maximal attempts. Having a precise figure at your fingertips empowers better planning and more confident decisions.
Epley Formula: 1RM = weight × (1 + reps / 30) Example: 225 lbs × (1 + 5/30) = 225 × 1.167 = 262.5 lbs Accuracy: Best for 2–10 reps. Tends to overestimate above 10 reps. For 1 rep input, 1RM = weight lifted (no formula needed).
Result: Estimated 1RM: 262.5 lbs
Lifting 225 lbs for 5 reps gives: 225 × (1 + 5/30) = 225 × 1.1667 = 262.5 lbs. This means your training percentages would be: 90% = 236 lbs, 80% = 210 lbs, 70% = 184 lbs, 60% = 158 lbs. These percentages help you plan sets across different training goals — strength (85–95%), hypertrophy (65–80%), and endurance (50–65%).
Boyd Epley developed his formula while serving as strength coach at the University of Nebraska in the 1980s. He needed a practical way to set training weights for football players without the time and injury risk of constant maximal testing. The formula's simplicity (just multiply by 1 + reps/30) made it easy for coaches to calculate on the fly, even without a calculator.
Retest every 4–6 weeks during a linear progression program, or at the start of each new training block in a periodized program. If your training weights feel significantly easier or harder than prescribed RPE, your estimated max may have shifted and should be retested. Avoid retesting during deload weeks or when fatigued from high-volume training.
The percentage chart is your training roadmap. For powerlifting peaking: work from 70% up to 95–100% over 8–12 weeks. For bodybuilding: stay primarily at 65–80% with higher volume. For athletic performance: use 75–85% with explosive intent. The chart allows coaches to prescribe precise training loads for any goal.
Studies show the Epley formula is typically within 5–10% of actual 1RM for trained individuals in the 2–10 rep range. Accuracy decreases above 10 reps, where it tends to overestimate. Individual variation exists — some people's rep-max relationship is naturally different from the formula's prediction.
At high reps (12+), fatigue increasingly becomes a cardiovascular and muscular endurance challenge rather than a pure strength limitation. The Epley formula assumes a linear relationship between reps and max strength, but at higher reps, other factors (lactic acid, glycogen depletion, mental fatigue) limit performance before true maximal strength is reached.
For 1–6 reps, both formulas give very similar results. For 7–10 reps, Brzycki tends to give slightly lower (more conservative) estimates. Most coaches recommend using the average of multiple formulas for the best accuracy. Our multi-formula calculator does this automatically.
The formula works best for compound barbell movements (bench press, squat, deadlift, overhead press). It's less accurate for isolation exercises, machine movements, and exercises with variable resistance. It was originally developed and validated for barbell exercises.
Common programming guidelines: Strength — 3–5 reps at 85–95% 1RM. Hypertrophy — 6–12 reps at 65–80% 1RM. Muscular endurance — 12–20 reps at 50–65% 1RM. Power — 1–3 reps at 80–90% 1RM with explosive tempo. These are starting points; adjust based on individual response.
You should go close to failure (within 1–2 reps of failure, called RPE 8–9) but not to absolute technical failure. Stopping 1 rep short gives a very similar estimate while being safer. If you stop 2–3 reps before failure, you'll underestimate your 1RM.