1RM Calculator: Estimate Your One-Rep Max From Any Set

Enter the weight and reps from one hard set, ideally three to six reps taken close to failure, and the calculator estimates the heaviest single you could lift today. A one-rep max (1RM) is the maximum weight you can lift for one repetition (definition); this calculator averages the Epley and Brzycki formulas, which usually land within a few percent of a tested bench or squat max for sets of 10 reps or fewer (deadlift estimates tend to run low). Use the estimate to set training weights and track progress, not as a record.

How do you use the 1RM calculator?

Enter the weight you lifted and the clean reps you completed, from a set that finished within one or two reps of failure. Sets of three to six reps give the most reliable estimate; stay at 10 reps or fewer because accuracy drops above that.

1. Enter the full load on the bar, including the bar, your reps, and the unit: lb or kg.
2. Use your heaviest hard set of the day, not a warm-up.
3. Count only reps with full range of motion and consistent form.
4. Enter one exercise at a time: a squat set predicts a squat max, not a leg-press max.

Choose a set that was genuinely hard. If you stopped with four reps left, the estimate will be low; record the reps you could have done or use an RPE calculator. For more options, see all of our lifting calculators. Research found that five-rep maxes predicted a one-rep max more accurately than 10- or 20-rep maxes, and concluded linear equations should use no more than 10 reps (Reynolds et al., 2006).

Which formula does the calculator use, and why do calculators disagree?

The headline estimate is the average of Epley and Brzycki, two common equations. The calculator also shows four other published equations and the spread between them because different formulas give different answers from the same set.

Epley: 1RM = weight × (1 + reps ÷ 30)
Brzycki: 1RM = weight × 36 ÷ (37 − reps)

Epley comes from Boyd Epley’s 1985 poundage chart; Brzycki was published by Matt Brzycki in 1993. They agree exactly at 10 reps; below that, Epley reads higher (formula comparison). The other equations shown are Lombardi, O’Conner, Mayhew, and Wathen (Mayhew et al., 2008). In a study of 220 men, researchers found Brzycki most accurate for sets of 10 or fewer and noted that averaging two equations may reduce error (Mayhew et al., 1995).

For 225 lb (102 kg) × 5:

• Epley estimates 262.5 lb.
• Brzycki estimates 253.1 lb.
• The headline estimate is 257.8 lb.

That roughly 10 lb spread comes from one set; the true max is usually somewhere in that band. One rep is already a max, so the calculator returns the weight itself. It accepts one to 12 reps and warns that estimates above 10 reps are less dependable.

How accurate is an estimated one-rep max?

It is accurate enough to train from, not to bet on. In a classic validation study of untrained college students, predicted and tested maxes correlated above r = 0.95 for bench, squat, and deadlift, yet all formulas underestimated the deadlift by 9–14% (LeSuer et al., 1997).

• Bench press: Most equations underestimated by 2.2–5.4 lb (0.8–6%); Epley’s average miss was about 1%.
• Squat: Equations underpredicted by 4.6–16.5 lb (2–8%).
• Deadlift: Every equation underpredicted by 22.2–33.7 lb (9–14%), so treat the estimate as conservative.

No one equation wins for everyone. A 2024 study found accuracy varied by lift and sex; Lombardi worked best for men’s bench and squat (Ribeiro et al., 2024). Showing a range is more honest than claiming one precise number.

Why is my estimate different from what I can actually lift?

Usually the set was not a true test of fatigue, or your rep-to-strength profile differs from the average assumed by the formula. Endurance-trained lifters can do many more reps at a given percentage, which can make a formula overestimate their max.

• You stopped early with reps in reserve → the estimate skews low.
• You entered 12 or more reps → the estimate can drift because formulas were built on 10 or fewer.
• You have a high-rep profile → at 70% of max, endurance runners did about 40 leg-press reps versus about 18 for weightlifters (Richens & Cleather, 2014).
• You rarely lift heavy singles → you may not be able to express the estimate on test day; novices may test below prediction.
• You entered a deadlift set → the estimate tends to be low.

How should you use your 1RM in training?

Use the estimate to choose working weights and track progress. Multiply it by a percentage to set loads, such as 80% for heavy sets of about eight; an AMRAP set can make a useful top set to track. For strength, ACSM’s 2026 position stand points to heavier loads around 80% of 1RM for two to three sets per exercise (ACSM guidelines).

The table compares Epley-derived reps with the NSCA chart (NSCA Training Load Chart), using the 257.8 lb headline estimate from 225 lb × 5. Working weights are rounded to 5 lb; reps above about 12 are loose guides.

Use a simple trend-line method:

1. Log one top set per main lift each week.
2. Compute the estimate the same way each time.
3. Watch the line across weeks, not one point; one bad day is noise, while three flat weeks is a signal.

Keep the formula, exercise, depth, and pause rules consistent or the trend loses meaning. For more on the rules that still work for getting stronger after year one, focus on repeatable training.

Should you test a true 1RM or just estimate it?

Estimate most of the time and test rarely. A true max needs a long warm-up, a spotter or safeties, and a fresh day; it spends a session proving strength instead of building it.

• Test when you compete, start a percentage-based program, or your estimate clearly disagrees with your actual lifts.
• A 3–5RM test is a useful middle ground: heavy enough to estimate well, safer than a single.
• For a true test, build up through light sets of 5–10, then 3–5, then 2–3 reps, resting one to four minutes and adding weight gradually (HPRC’s 1RM protocol).

What does it mean when your estimated max stops going up?

A flat estimate for three or more weeks of normal training usually means you have stalled, and the calculator cannot tell you why. Common causes include no progression rule, sets that end too early, testing more than training, too little practice, an untrained sticking point, or recovery that cannot keep up.

• Check whether you have a clear rule for adding weight.
• Make sure your working sets are hard enough and you practice the main lift often enough.
• Look at sleep, stress, and diet; each can limit recovery.

Most lifters have more than one cause, and fixing the wrong one first wastes time. Review how to keep progressive overload going when the weight won’t move. Log the estimate, and if it has not moved in a few weeks, find out which cause is holding your max back.

FAQ

Is the Epley or Brzycki formula more accurate?

Neither wins everywhere. They give the same answer at 10 reps, and below that Epley reads a few percent higher. Studies find the best equation varies by lift and lifter, so use both as a range and trust the estimate most when your set was three to six hard reps.

How many reps should I use to estimate my 1RM?

Three to six reps close to failure is the sweet spot, and stay at 10 or fewer. Research found five-rep maxes predicted a true max best and advised against using linear formulas beyond 10 reps (Reynolds et al., 2006). Above that, muscular endurance has more influence on the number.

Why does the calculator underestimate my deadlift?

It is a known pattern: in a classic validation study, every formula underestimated the deadlift by 9–14%, even though bench estimates were within a few percent (LeSuer et al., 1997). Treat the estimate as a conservative floor; use a heavy triple or tested single if you need an exact number.

How often should I test my one-rep max?

Rarely. Estimate from normal top sets every week or two and watch the trend; test a true single for a meet, before a percentage-based program, or when the estimate clearly disagrees with what you lift. A max-out day proves strength instead of building it.