Your one-repetition maximum — the heaviest weight you can lift for a single, clean repetition — is the reference point nearly every strength program is built around. It tells you how strong you actually are, sets the percentages for your working sets, and gives you a single number to chase as you train. But testing a true 1RM is nerve-racking, fatiguing, and carries real injury risk, especially when you are not warmed up or training alone.
This one-rep max calculator estimates your 1RM from a set you already completed. Enter the weight you lifted and the number of good reps you got, and it predicts your max with two of the most widely used formulas in strength coaching — Epley and Brzycki — then shows the training loads at 80%, 90%, and 95% of that estimated max. It works the same for the bench press, back squat, deadlift, overhead press, and barbell row, so you can rate any lift in your program.
How to Use
- Enter the Weight Lifted for a recent, hard set. Use the total load on the bar — the barbell plus all plates on each side — not the number you think you used.
- Set Reps Completed to the number of clean, full-range repetitions you finished before you could not complete another one. Stop counting sloppy, half-reps; they inflate the estimate.
- Pick the Exercise from the dropdown. The math is identical for every lift, but naming the move keeps your training loads organized across bench, squat, deadlift, overhead press, and row.
- Choose your Units — pounds or kilograms. The formula itself is unit-agnostic; the result simply carries the unit you selected.
- Read the result card. Estimated One-Rep Max is the blended prediction, with the Epley and Brzycki figures shown side by side so you can see how close the two formulas agree.
- Use the 80% / 90% / 95% Training Load lines to plan your next sessions. Roughly 80% is the classic hypertrophy working range, 90% builds maximal strength, and 95% is reserved for peaking or practicing heavy singles.
For the best estimate, test a set of between 2 and 6 reps. Predictions drift when you do 12+ reps with a light weight or when the reps are heavily assisted by bouncing, momentum, or a spotter.
The Formulas Behind the Number
Two regression equations dominate strength coaching, and they are both built from data collected on trained lifters:
Epley: 1RM = w × (1 + r / 30)
Brzycki: 1RM = w × 36 / (37 − r)
Where w is the weight lifted and r is the number of reps completed. On a set of 225 lb for 5 reps, Epley predicts 225 × (1 + 5/30) = 262.5 lb, while Brzycki gives 225 × 36 / 32 = 253.1 lb. This calculator averages the two into a single 257.8 lb estimate, because blending formulas smooths out the small bias each one carries at different rep counts.
Epley tends to be more accurate for heavier, lower-rep sets, while Brzycki stays close across a wider rep range. When the two results disagree by more than about 5%, treat that as a sign your reps were inconsistent — re-test with a cleaner set rather than trusting either number blindly.
Why Percentages Matter
Raw strength is rarely trained with a single rep. Programs from Starting Strength to 5/3/5 to Wendler's 5/3/1 organize work as a percentage of your 1RM:
- Around 80% of 1RM is the bread-and-butter working weight for sets of 5. It builds muscle and work capacity without trashing your nervous system.
- Around 90% is near-maximal territory, used for sets of 1–3 to drive raw strength gains.
- Around 95% is a heavy single. It belongs in peaking blocks or short practice sessions, not in weekly volume work.
If your estimated max is 258 lb, your 80% working load is about 206 lb, your 90% strength load is about 232 lb, and a 95% heavy single is about 245 lb. That conversion — from a single "what's my max" question into three usable training weights — is the real value of the calculator.
Examples
Example 1 — A hard bench press set. You bench 225 lb for 5 clean reps and miss the sixth. The Epley estimate is 262.5 lb, Brzycki is 253.1 lb, and the blended estimated one-rep max is 257.8 lb. Your next hypertrophy block should use about 206 lb for sets of 5, and you can practice a heavy single near 245 lb when you want to test yourself.
Example 2 — A heavy deadlift for triples. You pull 315 lb for 3 reps. Epley predicts 346.5 lb and Brzycki predicts 333.5 lb, for a blended deadlift 1RM of about 340 lb. Your 90% strength load works out to roughly 306 lb — a sensible weight for sets of 2–3 in a strength cycle.
Example 3 — A squat wall at 10 reps. You squat 185 lb for 10 reps. At 10 reps the two formulas begin to separate, and the estimate (about 247 lb) is a rougher guess than a 3–5 rep set. Treat it as a planning number, not a promise, and re-test with a heavier set of 3–5 reps before you program off it.
FAQ
What is a one-rep max (1RM)?
Your one-rep max is the maximum weight you can lift with good form for a single repetition of a given exercise. It is the baseline strength number that percentage-based programs use to set working weights. You do not have to actually attempt a max to estimate it — formulas like Epley and Brzycki predict it from a multiple-rep set.
Which formula is more accurate, Epley or Brzycki?
Neither is universally "best." Epley (1RM = w × (1 + r/30)) tends to track heavier, lower-rep sets most closely, while Brzycki (1RM = w × 36/(37 − r)) stays accurate across a broader range of reps. This calculator averages both because blending reduces each formula's individual bias. For the most reliable result, test a set of 2–6 reps rather than a high-rep pump set.
How many reps should I use to estimate my 1RM?
A hard set of 2 to 6 reps on a weight you could barely complete gives the tightest prediction. Predictions from very light sets of 10+ reps are less reliable because fatigue, technique breakdown, and muscular endurance distort the rep-to-max relationship. If your estimated max is for a competition or a formal peaking plan, confirm it with an actual low-rep test under a spotter.
What percentage of my 1RM should I train at?
It depends on the goal. About 80% of your 1RM is the classic hypertrophy range for sets of 5; roughly 90% builds maximal strength in sets of 1–3; and about 95% is a heavy single reserved for peaking or practice. Running weekly sets at 95%+ leads to unnecessary fatigue and injury risk, so reserve the heaviest percentages for short, planned blocks.
Does the calculator work for squat and deadlift too?
Yes. The Epley and Brzycki formulas are exercise-independent regressions on rep performance, so they apply the same way to the bench press, back squat, deadlift, overhead press, and barbell row. The only difference between lifts is your current level in each one — a 300 lb deadlift and a 300 lb bench press mean very different things about your development.
Should I switch between pounds and kilograms?
Pick whichever unit you train and log in. The math is unit-agnostic, so 225 lb and 102 kg give proportional estimates in their own units. Just be consistent: do not enter a set weighed in kilograms while the unit selector is set to pounds, or your percentages will be wrong by a factor of roughly 2.2.
Is an estimated 1RM as good as a tested 1RM?
An estimate is a planning tool, not a max attempt. It is usually within 3–5% of a true max for trained lifters on a good 3–5 rep set, but it is less reliable for novices, technical lifts, and very high rep counts. Use the estimate to program training weights; only attempt an actual 1RM when you are fully warmed up, practiced, and preferably spotting or bailed safely.
Disclaimer
This one-rep max calculator is provided for informational purposes only. It is a training-planning estimate based on the Epley and Brzycki regression formulas and the inputs you enter; it is not medical advice, and it does not replace the judgment of a qualified coach, athletic trainer, or physician. Estimates are less reliable for high-rep sets, beginners, or anyone with an injury. Always warm up thoroughly, use proper form, train with a spotter on heavy lifts, and stop if you feel sharp pain or joint discomfort.