One Rep Max Calculator
A one rep max calculator turns any working set into an estimated 1RM. Enter the weight you lifted and the reps you did — this tool runs three validated formulas (Epley, Brzycki, Lombardi), shows each result plus their average, and builds a full percentage training chart from 100% down to 50%.
Result
| Epley | |
| Brzycki | |
| Lombardi |
Percentage chart
Formula & source
Brzycki: 1RM = w × 36 / (37 − r)
Lombardi: 1RM = w × r0.1
Reported max = mean of the three
Sources: Epley (1985), Brzycki (1993), and Lombardi (1989) — the three most-cited rep-max formulas in strength literature. All three are rep-based estimates, most accurate for sets of 1–10 reps; beyond 12 reps the error grows and the calculator clamps reps to 12. Unique to this page: all three formulas are shown side by side instead of hiding behind one number, so you can see the spread and judge the uncertainty yourself.
Worked example (you can verify by hand)
Input: 225 lb × 5 reps.
- Epley: 225 × (1 + 5/30) = 225 × 1.1667 = 262.5
- Brzycki: 225 × 36 / (37 − 5) = 225 × 1.125 = 253.1
- Lombardi: 225 × 50.1 = 225 × 1.1746 = 264.3
- Average: (262.5 + 253.1 + 264.3) / 3 = 260.0
Expected output: estimated 1RM ≈ 260 lb; 90% row = 234 lb.
Limitations — what this cannot do
- Estimates, not measurements — only a true 1RM test (or meet total) is exact; formulas typically land within ±5% for sets under 10 reps.
- Technique, fatigue, sleep and warm-up change the real number day to day; retest or recalculate every 4–6 weeks.
- Not for beginners attempting maximal singles without a spotter and coaching — build base volume first.
Disclaimer: Estimates for training planning only, not medical advice. Consult a professional.
FAQ
Which 1RM formula is most accurate?
No single formula wins everywhere. Epley, Brzycki and Lombardi usually agree within a few percent for sets of 3–8 reps; that is why this calculator shows all three plus their average instead of hiding the spread.
How many reps should I use for a 1RM estimate?
Use a heavy set of 2–6 reps taken close to failure. Estimates from 10+ rep sets drift — the calculator clamps input to 12 reps for this reason.
What is a good 1RM percentage for strength vs muscle?
Roughly: 85–100% for maximal strength (1–5 reps), 65–85% for hypertrophy (6–12 reps), below 65% for warm-ups and volume. The percentage chart above labels each row.
Should I test my true 1RM instead?
If you compete or run a peaking block, yes — test it with proper warm-up, spotters and rest. For programming training blocks, a calculated 1RM is safer and usually close enough.