One Rep Max Calculator
Estimate your 1RM and training weights from any set.
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Your one-rep max (1RM) is the heaviest weight you can lift for a single clean repetition of an exercise. It is the reference point most strength programs are built around, because they prescribe working weights as a percentage of it. Testing a true max is tiring and carries some injury risk, so this calculator estimates your 1RM from a set you have already done: enter the weight and the number of reps, and it returns your predicted single, plus a table of training weights from 1 to 15 reps.
How the 1RM estimate is calculated
We average three well-known prediction formulas — Epley, Brzycki and Lombardi — rather than trusting any single one. Each reads the reps-to-failure relationship slightly differently, so averaging smooths out their individual quirks. Epley multiplies the weight by (1 + reps / 30), Brzycki by 36 / (37 − reps), and Lombardi by reps raised to the power 0.1.
For example, if you bench press 100 kg for 5 clean reps, Epley predicts 116.7 kg, Brzycki 112.5 kg and Lombardi 117.5 kg. The average is about 116 kg, which is your estimated one-rep max. The same method works in pounds — the formulas only multiply your input, so the units carry through unchanged.
How accurate is it, and when to use it
These formulas are most accurate for low-rep sets, roughly 1 to 6 reps. The further you go past that, the more the estimate drifts, because endurance and technique start to influence how many reps you can grind out. A heavy triple or set of five gives a far better prediction than a set of fifteen. For the closest number, use a recent set taken close to failure with solid form.
Treat the result as a working estimate, not a guaranteed lift. Your real max varies day to day with sleep, fatigue and warm-up quality, and it differs between exercises — your squat and deadlift estimates will not match. Use it to set training loads and to track progress over weeks rather than as a single number to chase on any given day.
Using the percentage table
Most strength programs are written as a percentage of 1RM — for instance 5 sets of 5 at 80%. The table turns your estimated max into concrete weights for each rep range so you do not have to do the math at the rack. With an estimated 116 kg max, 80% is about 93 kg for your sets of five, while 90% near 104 kg suits heavy triples and 70% near 81 kg suits higher-rep volume work.
How to use
- 01
Enter weight and reps
Type the weight you lifted and how many clean reps you got.
- 02
Calculate
We average the Epley, Brzycki and Lombardi formulas for your estimated 1RM.
- 03
Use the table
The percentage table shows training weights for 1–15 reps.
Frequently Asked Questions
Your 1RM is the maximum weight you can lift for a single repetition of an exercise with good form.
Estimates are most accurate for sets of 1–6 reps. Above 10 reps the error grows, so use lower-rep sets for the best estimate.
Estimating from a sub-maximal set avoids the fatigue and injury risk of a true max attempt.
Most strength programs prescribe a percentage of 1RM — for example 5 sets of 5 at 80% — and the table gives you those weights instantly.
Reference data
| Reps | %1RM |
|---|---|
| 1 | 100% |
| 2 | 95% |
| 3 | 93% |
| 4 | 90% |
| 5 | 87% |
| 6 | 85% |
| 8 | 80% |
| 10 | 75% |
| 12 | 70% |
| 15 | 65% |
How to Estimate Your One-Rep Max Without Testing It
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Last reviewed June 2026 · Methodology & sources