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 rep-based 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
Method and assumptions: Epley (1985), Brzycki (1993), and Lombardi (1989) are the named rep-based equations used here. The displayed mean is this site’s simple arithmetic summary of their estimates, not a separately validated prediction model. The spread compares equations; it is not a confidence interval for your lift. The estimate uses 1–12 reps; the calculation caps values above 12.
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
- These are estimates, not measured maximum lifts. Individual error depends on the exercise, lifter, technique and effort; this site does not establish a fixed accuracy range.
- 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?
This page does not establish which formula is most accurate for an individual. It shows each estimate and a simple arithmetic mean so you can compare the methods. Agreement between them does not establish the error relative to your actual lift.
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.