Estimate your one-rep max (1RM) in seconds

How the One-Rep Max Calculator Works

This calculator applies the two most widely used prediction formulas to estimate the maximum weight you could lift once based on a set you can actually complete. Enter the weight you lifted and the number of clean reps you managed, and it returns an estimated 1RM.

• Epley formula: 1RM = weight × (1 + reps/30).
• Brzycki formula: 1RM = weight × 36/(37 - reps).

Both formulas are validated for the bench press, squat, and deadlift by LeSuer et al. (1997), who found prediction equations accurate to roughly ±5-7% for sets up to 10 reps. The two methods usually agree within a few pounds, so we show both so you can see the range.

For quick reference, here is what a given number of reps represents as a percentage of your one-rep max:

The percent columns give you the same information backwards: if you want to run a set of 5 on a 300 lb estimated max, load roughly 86% of 300 lb (about 258 lb) per the Epley curve. That is how percent-based programs turn one estimate into a whole block of working weights.

The Math Behind the Formulas: Worked Examples

Both formulas are simple enough to do by hand, which is useful when you want to double-check the calculator or set loads without opening an app. Here are four worked examples across realistic rep ranges.

Example 1: 225 lb for 5 reps. Epley: 225 × (1 + 5/30) = 225 × 1.167 = 262 lb. Brzycki: 225 × 36/(37 - 5) = 225 × 36/32 = 253 lb. The two estimates sit 9 lb apart, within the normal noise of a heavy set.

Example 2: 200 lb for 3 reps. Epley: 200 × (1 + 3/30) = 200 × 1.10 = 220 lb. Brzycki: 200 × 36/34 = 212 lb. At low rep counts the spread is wider in percentage terms, which is why 3-rep maxes are usually just tested directly rather than estimated.

Example 3: 315 lb for 10 reps. Epley: 315 × (1 + 10/30) = 315 × 1.333 = 420 lb. Brzycki: 315 × 36/27 = 420 lb. Notice the formulas converge at exactly 10 reps; that is where the two fitted curves cross. A 420 lb estimate from a 315×10 set is why so many programs call 10-rep sets "70% work": the estimate assumes you could nearly triple the weight in a single rep.

Example 4: 100 lb for 12 reps. Epley: 100 × (1 + 12/30) = 140 lb. Brzycki: 100 × 36/25 = 144 lb. Above 10 reps the two diverge again, and both tend to overshoot because muscular endurance inflates what a high-rep set predicts. Treat any estimate from 12+ reps as a rough ceiling, not a training target.

One more useful pattern: the gap between the two formulas is informative by itself. When Epley and Brzycki agree closely (within a few pounds), the estimate is at its most trustworthy, and the mid-range where they cross near 10 reps is the point of maximum confidence. When they disagree by 10 lb or more, you are outside the reliable window, and the honest move is to test with a heavier, lower-rep set. The calculator flags this automatically in the result note: within a few pounds it tells you both formulas agree, and beyond that it asks you to treat the spread as your likely range.

Why Use an Estimated 1RM Instead of Testing?

Testing a true one-rep max is stressful on the joints, connective tissue, and nervous system, and it requires a spotter (for the bench) or careful setup (for squats and deadlifts). Estimating from reps lets you gauge strength progress every session without the risk. For a beginner, the estimate is also more honest than a max test: form that is still developing will flatter a heavy single, while a 5-rep set at a moderate weight reveals usable strength without loading a half-learned groove. The estimate is especially useful for:

• Programming training loads: Percent-based programs use 1RM to set working weights (e.g., 5×5 at 80% of 1RM).
• Comparing to standards: Plug your estimated 1RM into our bench press standards, squat standards, deadlift standards, or overhead press standards pages to see where you rank.
• Tracking progress: A rising estimated 1RM is the clearest single sign that your strength is improving, without needing to max out.

How Accurate Are These Formulas, Really?

LeSuer et al. (1997) compared seven prediction equations against actual 1RM testing in the bench press, squat, and deadlift and found the Epley and Brzycki equations among the most accurate across all three lifts. The headline number is ±5-7% for sets up to 10 reps. To translate that into pounds: on a 300 lb squat, 5-7% means your true max probably falls somewhere in a 285-321 lb window around the estimate. That is plenty precise for setting training loads, and it is far better than guessing.

Reynolds et al. (2006) confirmed that rep-based prediction from sets of 2-10 reps is reliable for resistance-trained men and women, with accuracy declining above 10 reps. The ACSM (2009) endorses estimating 1RM from submaximal sets as a safe alternative to maximal testing for most exercisers, especially beginners and older adults. None of the equations is perfect, but the error is small enough that coaches have trusted them for decades.

When the Estimates Break Down: Sets Over 10 Reps

The formulas assume that the weight you can lift decays at a predictable rate as reps climb, and that assumption holds from 1 to about 10 reps. Past 10, a different physiology takes over. A 15-rep set of squats is limited by local muscular endurance, lactic acid clearance, and cardiovascular capacity, not by maximal force production. The formulas cannot see that difference, so they extrapolate a strength curve from data that is no longer purely about strength.

The practical consequences: estimates from 10-15 reps overshoot your true 1RM by 5-10%, and estimates from 15+ reps become meaningless. A lifter who squats 225 lb for 15 might get an Epley estimate of 337 lb, but no honest coach believes that lifter can squat 337. If your best working set is over 10 reps, either do a heavier, lower-rep set (3-6 reps is the sweet spot) or accept that the number is an upper bound, not a plan.

What Affects the Accuracy of Your Estimate

• Rep range: Most accurate for 1-10 reps. Above 10 reps, muscular endurance contaminates the estimate.
• Lift and technique: Formulas were validated on the bench, squat, and deadlift. For the overhead press, error is slightly higher because the lift is more technique- and mobility-dependent.
• Training status: Well-trained lifters show slightly lower error than novices, whose form may limit the reps achieved.
• Fatigue and motivation: Testing on a fatigued day underestimates true strength. Test fresh, after a deload or rest day.
• Your last rep: Use the heaviest set you complete with good form, not a grind-to-failure set with compromised technique.

How to Get a Reliable Estimate

1. Warm up with 3-4 ramp-up sets (e.g., 50%, 65%, 75%, 85% of your estimated max).
2. Select a weight you can lift for 3-10 reps with good form and 1-2 reps left in reserve.
3. Perform one all-out set to near-failure and record the exact weight and reps.
4. Enter those two numbers here to get your estimated 1RM from both formulas.
5. Compare your estimated 1RM against published standards for your body weight using our strength standards pages.

How to Test a True 1RM Safely

Sometimes you want the real thing, and a properly run max-out day is safe if you follow a few rules. First, never walk in and take your top weight: ramp through singles at roughly 50%, 70%, 80%, 85%, 90%, then 95%, taking 2-3 minutes of rest between the heavy attempts. Second, always use a spotter for the bench press and safety pins in a rack for the squat; deadlifters should pull on a platform so a dropped rep lands flat. Third, take at least three working attempts, adding 2-5% each time until you fail, and stop after the first miss. Your 1RM is the last weight you completed with full range of motion.

Plan max attempts after a deload week, when your nervous system is fresh, and expect the number to be roughly 5% lower than an estimate from a good 5-rep set. That gap is normal; the estimate and the test measure slightly different things.

Check Your 1RM Against Strength Standards

Once you have an estimated 1RM, the next question is usually "is that good?" Our bodyweight-stratified standards pages answer exactly that, classifying a lift as beginner, novice, intermediate, advanced, or elite:

• Bench press standards by body weight
• Squat standards by body weight
• Deadlift standards by body weight
• Overhead press standards by body weight

For a quick relative-strength view, also try our strength-to-weight ratio calculator.