Which 1RM formula is the most accurate — Epley, Brzycki, or Lombardi?

No single formula wins across all rep ranges and individuals. Brzycki tends to be most accurate for low rep sets (1–6 reps), which is the range most strength athletes test in. Epley is the most widely cited and works well across moderate rep counts. Lombardi is the most conservative and holds up better at higher rep counts. Averaging all three, as this calculator does, gives the most balanced estimate for general use.

How many reps should I use for the most accurate 1RM estimate?

The sweet spot is 3–6 reps with a weight you could do maybe 1–2 more with perfect form. All three formulas are most reliable in this range. Going beyond 10 reps introduces significant error — fatigue, cardiovascular limitations, and technique breakdown all affect the result in ways the formulas don't fully account for.

Can I use this calculator for any exercise, or just compound lifts?

You can apply it to any exercise, but results are most meaningful for compound barbell lifts like squat, bench press, and deadlift. For isolation exercises like curls or lateral raises, the 1RM concept is less useful for programming purposes, though it still gives you a relative strength benchmark. Consistency matters most — always test the same variation with the same technique.

My actual 1RM test came out lower than the calculator predicted. Why?

Several factors can cause this: testing on a fatigued day, psychological barrier near true max loads, poor technique under maximal tension, or simply that your muscles are more fatigue-resistant than the average the formulas model. The formulas assume a standard strength-endurance curve, but lifters with higher slow-twitch fiber proportions can often rep out more at submaximal weights, causing the formulas to overestimate their true 1RM.

How often should I retest my 1RM?

In a structured training program, most coaches recommend retesting every 4–12 weeks — roughly once per training block. Retesting too frequently disrupts your program since heavy max-effort work is taxing. Some programs use a calculated 'training max' (90–95% of estimated 1RM) as the programming anchor specifically to avoid over-relying on exact 1RM tests.

Is it safe to attempt an actual 1RM lift, or should I just use the calculator?

For experienced, well-coached lifters: yes, testing an actual 1RM periodically is fine and provides the most accurate number. For beginners or those without a spotter, estimated 1RM from a submaximal set is safer and still very useful for programming. Always work up to a true max attempt gradually (incremental warm-up sets), have a spotter or safety equipment in place, and never attempt a true max when fatigued.

One-Rep Max (1RM) Calculator

Estimate your max single-lift strength from any working set.

Weight Lifted

Unit

Reps Performed

Estimated 1-Rep Max

— kg

Epley

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Brzycki

—

Lombardi

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Training Percentage Table

% of 1RM	Weight	Typical Use

Estimates based on average of Epley, Brzycki & Lombardi formulas. Most accurate for 1–10 reps. Always lift with a spotter near your true max.

Why Knowing Your 1RM Changes How You Train

Most lifters track their workouts by feel — "that felt heavy," "I had one more in me," "I think I'm stronger than last month." But without a reliable number to anchor your training, progress is guesswork. Your one-rep max (1RM) is the single most useful data point in strength training: everything from loading percentages to periodization cycles to competition attempts flows from it. The problem is that actually lifting your true 1RM carries real injury risk, especially without a coach or spotter. That's where estimation formulas come in.

The Three Formulas and What Makes Each One Different

When you lift a submaximal weight for multiple reps, that effort contains information about your top-end strength. Three well-tested equations extract that information in slightly different ways.

Epley (1985) is the oldest and most widely cited: 1RM = Weight × (1 + Reps/30). It's linear — every additional rep adds a fixed fraction of the lifted weight to the estimate. It tends to be slightly generous at higher rep counts, which is worth knowing if you're testing with sets of 8 or more.

Brzycki (1993) takes a different approach: 1RM = Weight × 36 / (37 − Reps). The denominator shrinks as reps increase, so the estimate climbs steeply when you get above 10 reps. Within the 1–6 rep range that most strength athletes actually test in, Brzycki is considered highly accurate and is the formula favored in many powerlifting coaching circles.

Lombardi (1989) uses a power function: 1RM = Weight × Reps^0.10. The 0.10 exponent means it climbs more gently than the other two, giving it a reputation as a conservative estimate. Some coaches prefer it precisely because an underestimate is safer than an overestimate when loading up for a near-max attempt.

Averaging all three — which is what this calculator does — tends to produce the most balanced result across different rep ranges and individual muscle fiber compositions. No single formula was derived from a population that includes every body type and training background, so a simple average hedges against any one equation being systematically off for your particular physiology.

How to Get a Reliable Test Set

The accuracy of any 1RM estimate is only as good as the set you test from. A grinding, form-breakdown set of 8 gives you a much noisier number than a controlled, technical set of 5 where you stopped with one or two reps in reserve. A few practical points:

Test in the 3–8 rep range whenever possible. All three formulas become progressively less reliable beyond 10 reps. Lombardi holds up better at higher rep counts, but even it drifts as fatigue and technique breakdown become confounding factors.
Warm up properly. A cold test set underestimates your strength. Work up through progressively heavier warm-up sets — roughly 40%, 60%, 80% of your expected working weight — before your test set. Rest 3–5 minutes between heavy sets.
Stop shy of failure. A rep that you barely grind out with poor form tells the formula something different than a rep completed cleanly. Aim for a set where you leave 1–2 reps in the tank; the estimate will be more consistent across sessions.
Use the same exercise consistently. Your squat 1RM estimated from a paused squat test will differ from one estimated via touch-and-go. Pick one style and stick with it for comparisons to mean anything.

Reading the Percentage Table

Once you have your estimated 1RM, the percentage table transforms it into a full programming tool. Strength training is built on the relationship between intensity (percentage of 1RM) and the rep ranges it supports. Here's how to think about each zone:

90–100% is your maximum strength zone. Sets here are almost always singles, doubles, or triples. This is where peaking phases live — the weeks before a competition or a test day when you're deliberately exposing your nervous system to near-maximal loads. Volume is low; frequency is carefully managed.

75–90% is the primary strength-building range. Most linear progression programs — Stronglifts, Starting Strength, Texas Method — spend the bulk of their time here. You're lifting heavy enough to force neural adaptations and strength gains, but the rep ranges (4–8 typically) allow enough volume to also build the muscle mass that underpins long-term strength.

60–75% is the hypertrophy zone. This is where bodybuilding-style programs and many muscle-building blocks of periodized strength programs operate. The higher rep counts (10–15+) create more metabolic stress and mechanical tension per set, which drives muscle growth efficiently — but with less direct carryover to 1RM performance than heavier loading.

Below 60% is mostly reserved for warm-ups, technique work, and conditioning. There are exceptions — very high-rep sets to failure at 50–55% can produce hypertrophy, as recent research on "myo-reps" and high-rep training has shown — but this range is rarely the focus of a primary strength or size block.

Common Mistakes When Using 1RM Estimates

The number coming out of a formula is an estimate, not a measured fact. Treating it with too much precision causes problems. Here are the mistakes worth avoiding:

Taking a first-attempt competition total from an untested estimate. If you're competing in powerlifting or Olympic weightlifting for the first time, your opening attempt should be something you know you can hit — ideally something you've actually done in training. A formula result based on a single training set isn't the same confidence level as a weight you've moved three times this month.

Ignoring how daily variation affects the test. Sleep, hydration, stress, and whether it's your first or third training day in a row all affect output by 5–10%. An estimate taken on a depleted day will underestimate you; one taken on your best day ever might overestimate what you can hit consistently.

Recalculating too frequently. Your 1RM estimate should inform training across a block of several weeks, not shift every session. Pick a test day, get a good number, program off it for 4–12 weeks, then retest.

Practical Example: Bench Press Programming

Say you bench press 90kg for 6 clean reps. The calculator gives you estimates of roughly 108kg (Epley), 104kg (Brzycki), and 108kg (Lombardi), averaging around 107kg. You round conservatively to 105kg as your working 1RM.

From there: a 4x5 strength block runs at 80% — so 84kg per set. A 3x8 hypertrophy block runs at 72.5% — about 76kg. A peaking week double runs at 90% — 94.5kg, which you'd round to 95kg. Every week of training becomes a calibrated step toward a tested, real 1RM — not a random weight chosen by feel.

That's the real value of the estimate: not the number itself, but the structured training it enables. Precision in the gym compounds over months and years into strength that guesswork never builds.

🏋️ One-Rep Max (1RM) Calculator