Article — One Rep Max Calculator (1RM)
One Rep Max Calculator
One rep max (1RM) is the most weight you can lift for a single full-range repetition. It is estimated from a submaximal set by two standard formulas: Epley (1985), 1RM = w × (1 + r/30), and Brzycki (1993), 1RM = w × 36/(37 − r). For 225 lb × 5 reps, Epley gives 262.5 lb and Brzycki 253.1 lb.
The calculator on this page runs both formulas, averages them, and prints a 50-95% training-weight table for every common percentage. Below are the details: where the formulas come from, when each is more accurate, and how to use the 1RM number in a real training plan.
What is one rep max?
One rep max is the maximum weight a lifter can move through the full range of a given exercise for a single repetition with correct form. It is the upper anchor of every strength-training program. Periodized programs are built around percentages of 1RM: 70-80% for hypertrophy blocks, 80-90% for strength blocks, 90-100% for peaking and testing.
Testing 1RM directly is the gold standard, but it is risky and tiring. A failed max attempt can pull a muscle, tweak a back, or cost a week of recovery. So most lifters estimate 1RM from a recent set of 2-10 reps using one of the formulas below. The estimate is accurate to ±3-5% for sets in that range, which is precise enough for programming.
The two main one rep max formulas
Boyd Epley, the longtime strength coach at the University of Nebraska, published his formula in 1985 as part of a training manual. It is the simpler of the two: 1RM = w × (1 + r/30). For 225 lb at 5 reps, that gives 225 × 1.1667 = 262.5 lb.
Matt Brzycki published his formula in the Journal of Physical Education, Recreation & Dance in 1993. It uses a hyperbolic curve: 1RM = w × 36/(37 − r). For 225 lb at 5 reps, that gives 225 × 36/32 = 253.1 lb. Brzycki is more conservative at low reps and more aggressive at high reps. It diverges at 37 reps because the denominator hits zero.
The LeSuer 1997 study in the Journal of Strength and Conditioning Research compared seven 1RM prediction formulas — Epley, Brzycki, Lander, Lombardi, Mayhew, O'Connor, and Wathan — across the squat, bench press, and deadlift in college athletes. Every formula was within 5% of true 1RM for 2-10 rep sets. None was decisively better.
Epley vs. Brzycki: which one rep max formula to use
For 1-5 reps, Epley and Brzycki agree within 1-2%. For 6-10 reps, they spread to 3-5 lb. Above 10 reps the gap widens, with Epley climbing faster. The Reynolds 2006 study in NCAA athletes found Brzycki slightly more accurate for lower-body lifts (squat, deadlift) and Epley slightly more accurate for upper-body lifts (bench, overhead press).
In practice, most coaches use the average of the two as the working 1RM. The calculator above reports both formulas plus the average. If you only want one number, use the average.
r = 1 225 lbr = 3 247 lb (Epley)r = 5 263 lb / 253 lbr = 8 285 lb / 279 lbr = 10 300 lb / 300 lbr = 12 315 lb / 324 lbUsing one rep max in programming
Once you have an estimated 1RM, the rest of the program follows. A hypertrophy block runs at 70-80% of 1RM for sets of 8-12. A strength block runs at 80-90% for sets of 3-6. A peak runs at 90-95% for sets of 1-3 in the lead-up to testing. The calculator's percent-1RM table maps the numbers directly.
The popular 5/3/1 program by Jim Wendler uses 90% of 1RM as the "training max" — the actual 1RM minus a buffer — and works waves of 65/75/85%, 70/80/90%, and 75/85/95%. The Texas Method uses similar percentages with weekly intensity ramps. Whichever program you follow, the 1RM number anchors the calculations.
Testing vs. estimating one rep max
Direct 1RM testing is rare in everyday training. A typical protocol warms up with 5 reps at 50%, 3 reps at 70%, 1 rep at 85%, 1 rep at 95%, then attempts 100% or higher. Rest is 3-5 minutes between top sets. A spotter or safety pins are mandatory on bench and squat.
Most lifters test 1RM every 8-12 weeks at most — at the end of a training cycle or before a meet. Between tests, the formulas in this calculator are the standard way to track strength progress without the recovery cost.
The most reliable way to estimate 1RM is to use a 3-5 rep set, where the last rep was a true grinding failure. Higher-rep sets introduce more form drift, more fatigue from accessory muscles, and more measurement noise. If you do "5 reps in reserve" sets, add 2-3 reps to your reported count before plugging into the formula.
One rep max standards by lift
Strength standards are exercise-specific. NSCA references for adult men: bench press 1.0× body weight is intermediate, 1.5× is advanced, 1.75× is elite. Squat is 1.5× / 2.0× / 2.5×. Deadlift is 1.75× / 2.5× / 2.75×. Overhead press is 0.55× / 0.85× / 1.1×. Women's values are about 65-75% of male values at the same body weight.
These standards drift with body-weight class. Lighter lifters tend to hit higher ratios because absolute strength scales sub-linearly with body mass. Federations use the Wilks or DOTS coefficient to compare lifters across weight classes; both are based on regression curves fit to thousands of meet performances.
Common mistakes with 1RM estimates
Reporting reps inaccurately is the biggest source of error. If you stop one rep short of failure, the formula underestimates your true 1RM. If you grind a sloppy final rep, the formula overestimates. Be honest about the last clean rep.
The second mistake is applying 1RM math to high-rep sets. A 20-rep set with light weight tests endurance, not strength, and the formulas drift badly. Stay in the 2-10 rep range for reliable estimates.
If you have been lifting less than 3-6 months, your reported "rep max" is dominated by technique inconsistency, not by actual muscular failure. The formulas give numbers, but those numbers are not stable yet. Focus on linear progression (add 5 lb per session) instead of percentage-based programming until you can grind out true sets.
A one rep max cheat sheet
- Epley = w × (1 + r/30)
- Brzycki = w × 36 / (37 − r)
- Best rep range = 2-10 reps for accuracy
- Test frequency = every 8-12 weeks at most
- Hypertrophy block = 70-80% × 8-12 reps
- Strength block = 80-90% × 3-6 reps
- Peak block = 90-95% × 1-3 reps
- Brzycki limit = diverges at 37 reps