Your one-rep max — the heaviest weight you can lift for a single, full-range repetition — is the reference point almost every strength program is built around. Progressive overload, percentage-based training blocks, and even powerlifting meet prep all start from a 1RM number. Testing a true 1RM on the platform is fatiguing, technique-sensitive, and risky, so coaches almost always estimate it from a set you can already complete. This 1RM calculator takes the weight and reps from a recent set and estimates your max using the two most widely used regression formulas, then extends the result into a full rep-max ladder you can plan training around.
Type in the load on the bar and the number of clean reps you finished, switch between pounds and kilograms, and every figure updates instantly. The result card shows the Epley and Brzycki estimates side by side, their average, and the derived 2RM, 5RM, 10RM and 20RM weights you should be able to hit in the same lift.
How to Use
- Enter the Weight Lifted — the total load on the barbell for the set, including the bar itself and all plates. If you benched 225 lb for 5 reps, type 225.
- Enter the Reps Completed — the number of clean, full-range repetitions you finished before you knew you could not do another. Do not count partial reps or sets stopped by spotter pressure; the estimate degrades quickly when reps are misreported.
- Pick your Units — pounds (lb) or kilograms (kg). The underlying math is unit-agnostic, so every output carries the unit you selected.
- Read the Epley 1RM as the primary estimate. It is the most commonly cited formula in commercial strength coaching and tends to track well across moderate rep ranges.
- Compare it with the Brzycki 1RM below it. Brzycki is more conservative at higher rep counts, so a wider gap between the two is a signal that your set was taken deep enough that the regression is less certain.
- Use the Rep Max Ladder — 2RM, 5RM, 10RM, 20RM — as ready-made working weights. A 5RM set is your hypertrophy anchor, a 10RM is your volume anchor, and a 20RM is your endurance anchor for the same lift.
For the most reliable estimate, base the calculation on a set of 3 to 8 reps taken close to failure. Estimates from single reps or from sets above 12 reps drift because the regression was fit on mid-range rep data.
The 1RM Formulas
Two formulas dominate strength coaching, and both come from linear regressions of actual max attempts against submaximal set data:
- Epley (1985): 1RM = w × (1 + r / 30)
- Brzycki (1982): 1RM = w × 36 / (37 − r)
Where w is the weight lifted and r is the number of reps completed.
On a 225 lb bench for 5 reps, Epley gives 225 × (1 + 5/30) = 262.5 lb, while Brzycki gives 225 × 36 / 32 = 253.13 lb. The average lands near 257.81 lb. Epley runs slightly higher because its slope is more forgiving as reps climb, while Brzycki pulls the estimate down faster — which is why Brzycki is preferred when the input set is deep.
The rep-max ladder is built by inverting the Epley formula. Once you know the estimated 1RM, the weight you should handle for k reps is 1RM / (1 + k/30). That lets you answer "what should I work up to for triples?" without re-testing.
Examples
Example 1 — A standard bench estimate. A lifter presses 225 lb for 5 clean reps. The calculator returns an Epley 1RM of 262.5 lb, a Brzycki 1RM of 253.13 lb, and an average estimate of 257.81 lb. The rep ladder shows a 246.09 lb double, a 225 lb set of five (which checks out against the input), a 196.88 lb ten, and a 157.50 lb twenty. A sensible next week of work is triples at 90% of the estimated 1RM, roughly 232 lb, and fives at 80%, roughly 206 lb.
Example 2 — A deep squat set. A lifter squats 315 lb for 8 reps. Epley estimates 315 × (1 + 8/30) = 399 lb, Brzycki estimates 315 × 36 / 29 = 391 lb, and the average sits around 395 lb. Because the rep count is high, the 8 lb gap between formulas is normal; trust the lower Brzycki figure when programming singles, and treat both as a range.
Example 3 — A heavy single attempt. A lifter deadlifts 405 lb for 2 reps. Epley gives 405 × (1 + 2/30) = 432 lb, Brzycki gives 405 × 36 / 35 = 416.57 lb. For low-rep inputs the two formulas converge, so the average near 424 lb is a reasonable planning max, and a first true attempt at 425–430 lb is realistic.
Example 4 — Large training load. On a platform where loads are tracked in metric, a 200 kg deadlift for 3 reps estimates to about 220 kg on Epley and 212 kg on Brzycki — a useful planning ceiling without walking out a heavy opener on meet day.
FAQ
What is a 1RM?
A 1RM, or one-rep maximum, is the heaviest weight you can lift with good form for exactly one repetition of a given exercise. It is the reference strength number used to set percentage-based training loads, to track progress over months, and to set opening attempts in powerlifting meets.
How accurate is an estimated 1RM?
Estimates from sets of 3 to 8 reps are typically within 3–5% of a true tested 1RM for experienced lifters. Estimates from a single rep are very accurate because the regression is close to identity, while estimates from sets above 10 reps drift upward because the formulas were not fit on deep, fatigued sets. Use a 3–8 rep set for the tightest estimate.
Epley vs Brzycki — which should I trust?
They are both valid and usually agree within a few percent. Epley is more common in commercial coaching and slightly higher at higher reps; Brzycki is more conservative and preferred when your input set is deep (6+ reps). When the gap is wide, plan training off the lower number to leave margin.
What is a rep-max ladder?
A rep-max ladder lists the weights you should be able to handle for different repetition counts — a 2RM, 3RM, 5RM, 10RM, 20RM — all derived from a single estimated 1RM. It turns one number into a week of programmable sets: heavy doubles for peak strength, fives for hypertrophy, tens for volume, twenties for muscular endurance.
Should I test a true 1RM instead of estimating?
Estimating is safer and less fatiguing for regular training. Test a true 1RM only occasionally — every 8–12 weeks, or ahead of a meet — and always after a proper warm-up, with a spotter, and when you are fresh. Estimation between tests is how most lifters actually train.
Does the exercise matter — bench, squat, deadlift?
The formula is the same for every lift because it only relates weight to reps. The number you get is specific to the exercise you performed: a 262 lb bench 1RM has no direct relationship to your squat 1RM. Re-run the calculator separately for each lift you want to program.
Disclaimer
This 1RM calculator is provided for informational purposes only and is not medical advice. Estimates come from the Epley and Brzycki regression formulas and are planning approximations, not tested maxima. Lifting heavy weights carries inherent risk of injury, especially when performing maximal or near-maximal attempts. Warm up thoroughly, use appropriate form, work within your current ability, and consult a qualified coach or healthcare professional before beginning or advancing any strength-training program.