What is a one rep max (1RM)?

A one rep max is the heaviest weight you can lift for a single repetition with good form. It is the standard measure of maximal strength for a lift, and training programs use percentages of it to set working weights.

Which formula is more accurate: Epley or Brzycki?

Neither is universally better. The Epley formula usually gives a slightly higher number and works well across a wide rep range, while Brzycki tends to be more conservative at higher reps. Both are within a few percent of each other below 10 reps, which is why this calculator also shows their average.

Why do the formulas lose accuracy above 10 reps?

Both formulas assume a fairly linear relationship between reps and the percentage of your max, which holds for heavy sets of 1 to 10 reps. Beyond about 10 reps, fatigue and muscular endurance play a bigger role, so the formulas can overestimate your true one rep max. For the most reliable estimate, test with a heavy set of 3 to 8 reps.

How do I use the 90%, 85%, and 80% numbers?

These are common training loads. Around 90% of your 1RM is typical for heavy strength sets of 1 to 3 reps, 85% suits sets of 4 to 6 reps, and 80% is a common range for hypertrophy-style sets of 6 to 10 reps. Use them as starting points and adjust to your program.

Should I test my true one rep max directly?

Only with proper preparation: a thorough warm-up, a spotter you trust, and good technique. A true max attempt is fatiguing and carries injury risk, which is exactly why estimation formulas exist. Most lifters test a max only a few times per year and use estimates the rest of the time.

One Rep Max Calculator

Estimate your one-rep max from any lift using the Epley and Brzycki formulas. Get training loads at every percentage, a rep-max table for 1–12 reps, and a side-by-side formula comparison.

Weight lifted

Weight unit

Repetitions performed

Estimates are most accurate at 10 reps or fewer.

Advanced options

Base the training loads on

Your body weight (lb) — optional, for strength ratio

Plate loader: working weight (lb)

Leave blank to load plates for your estimated 1RM average.

Bar weight (lb)

Plates you own (per side), comma-separated

Biggest plates first from this list (greedy loading).

Epley vs Brzycki — which formula?

Both formulas estimate your one-rep max from a submaximal set, but they weight reps differently. Epley (weight × (1 + reps/30)) treats every rep as adding a fixed 1/30th of the load — simple and slightly generous at higher reps. Brzycki (weight × 36/(37 − reps)) curves upward more aggressively and tends to read a little lower in the 3–8 rep range. Neither is "true"; your real 1RM depends on technique, fatigue, and the lift. The calculator shows both plus their average, which smooths out each formula's bias.

How to use the training-load table

Strength programs prescribe loads as percentages of your 1RM: roughly 85–95% builds maximal strength (1–5 reps), 70–85% builds a mix of strength and size (6–12 reps), and below 70% favors endurance and technique work. Pick the base formula in Advanced options, find your target percentage in the table, and load the bar to the listed weight. Round to the nearest plate you actually own — being 2 lb off the spreadsheet number never mattered.

Frequently Asked Questions

How accurate is a 1RM estimate?

Good enough for programming, not exact. Both formulas are calibrated on sets of roughly 2–10 reps; beyond 12 reps the estimates drift high. Technique, rest, and the specific lift all move your true max a few percent either way — treat the average as a working number and adjust from how the weights feel.

Why do Epley and Brzycki disagree?

They make different assumptions about how fast strength drops off per rep. Epley is linear (each rep adds 1/30 of the load); Brzycki curves. At 5 reps on 225 lb, Epley gives 262.5 and Brzycki 253.1 — about a 3.6% spread, which is normal.

Should I test my true 1RM instead?

Testing a true max is the gold standard but carries injury risk and needs a full warm-up, spotters, and experience with heavy singles. For most lifters, an estimate from a hard set of 3–5 reps plus the training-load table is safer and plenty accurate for programming.

What does the strength-to-weight ratio mean?

Your estimated 1RM divided by your body weight. A 1.5× bodyweight squat or 1× bodyweight bench press are common intermediate milestones. Enter your body weight in Advanced options to see yours.

Can I use this for any lift?

The math works for any lift, but the formulas were validated mostly on barbell presses and squats. They transfer poorly to single-joint or machine movements where rep 8 feels nothing like rep 3 — use extra caution there.

Estimates only — not medical advice. Lift with proper form and spotters.

One Rep Max Calculator

Epley vs Brzycki — which formula?

How to use the training-load table

Frequently Asked Questions

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