One-Rep Max Calculator
Estimate a one-repetition maximum by four named formulas, so the spread between them is visible.
Runs entirely in your browser. Nothing is uploaded, logged or stored.
Estimated maximum, as a range
120 – 126.7
- Middle of the four
- 123.5
- Each formula
- epley 126.7 (Epley, 1985 — w × (1 + r / 30)) brzycki 124.1 (Brzycki, 1993 — w × 36 / (37 − r)) lombardi 123.1 (Lombardi, 1989 — w × r^0.10) oconner 120 (O'Connor et al., 1989 — w × (1 + 0.025 r))
- Training percentages
- 95% — 117.3 90% — 111.1 85% — 105 80% — 98.8 75% — 92.6 70% — 86.4 65% — 80.3 60% — 74.1
- Inside the reliable range?
- yes
How much you could lift once, estimated from a set you actually did. Four published formulas are shown together rather than one alone, because they disagree — and the disagreement is the honest answer.
How it works
Epley, Brzycki, Lombardi and O'Connor each fitted a curve to the relationship between load and repetitions. At eight repetitions they can differ by five per cent or more of the estimate, which is why a single figure would be misleading. The range is the result; the middle is a convenience.
All four assume the set was taken close to failure. A set of eight you could have made twelve tells you nothing about your maximum, and no formula can detect the difference.
Past about ten repetitions the relationship stops being linear enough for any of them and the estimates fan out. The page says when you are outside that range rather than answering as though you were not.
The percentage table is built from Epley inverted, because that is the one most training programmes are written against.
Examples
| Case | Input | Result |
|---|---|---|
| A set of eight | 100 × 8 | 120 – 126.7 — a 5.6 % spread |
| A heavy triple | 140 × 3 | 148.2 – 154 — much tighter |
| A single | 150 × 1 | 150 — it already is the maximum |
Frequently asked questions
Which formula should I use?
None of them on its own. The four are shown together because they disagree, and the width of the disagreement tells you how much confidence the number deserves. At three repetitions they nearly agree; at twelve they do not.
Why does a single repetition return the weight itself?
Because it is the maximum, by definition. Epley and O'Connor return something slightly above the weight at one repetition, which is an artefact of fitting a curve rather than a claim about the lifter; Brzycki and Lombardi give the weight exactly.
Should I test my actual maximum instead?
That depends on why you want it. A true single is the only way to know, and it carries a risk and a recovery cost that a set of five does not. For writing a programme, an estimate from a hard set of three to five is usually enough and considerably cheaper.
Kilograms or pounds?
Whichever you train in. Every formula here multiplies the weight by a factor, so the unit passes straight through untouched.
Good to know
- These are estimates fitted to other people's lifting, and individual variation is large. Nothing here is advice about what you should attempt.
Sources
- Epley B. Poundage chart. In: Boyd Epley Workout. Lincoln, NE: Body Enterprises, 1985.
- Brzycki M. Strength testing — predicting a one-rep max from reps-to-fatigue. Journal of Physical Education, Recreation & Dance, 1993;64(1):88–90.
- Lombardi VP. Beginning Weight Training: The Safe and Effective Way. Dubuque, IA: Wm. C. Brown, 1989.
- O'Connor R, Simmons J, O'Shea P. Weight Training Today. St Paul, MN: West Publishing, 1989.