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One Rep Max Calculator
Estimate your one-rep max (1RM) from a set of reps with the Epley, Brzycki and Lombardi formulas, plus training loads from 100% to 50%.
Your one-rep max, or 1RM, is the heaviest weight you can lift once with good form. Strength programmes use it to set training loads — for example, sets of five at 85% of your max. Testing a true max is tiring and carries some risk, so most lifters estimate it from a heavier set of a few repetitions instead.
Enter the weight you lifted and how many reps you managed, and this calculator estimates your 1RM with three well-known formulas — Epley, Brzycki and Lombardi — and their average. A table then shows the weight for every percentage from 100% down to 50%, with the number of reps you can usually do at each. Works with kilograms or pounds; nothing is stored or sent.
How to use One Rep Max Calculator
- Choose kilograms or pounds.
- Enter the weight you lifted.
- Enter how many clean repetitions you completed.
- Read your estimated 1RM and the training-load table.
Features
- Epley, Brzycki and Lombardi estimates and their average.
- Training loads from 100% to 50% of 1RM.
- Typical reps at each percentage.
- Kilograms (rounded to 0.5) or pounds.
- Works for any lift: bench, squat, deadlift, press.
- Runs in your browser; nothing is stored or sent.
The formulas
Each formula describes how the weight you can lift falls as the number of reps rises. They agree closely for low reps and drift apart as reps increase, which is why the calculator shows all three and uses their average. Estimates are most reliable from sets of about 2 to 10 reps; the calculator accepts up to 12.
| Formula | Equation | Notes |
|---|---|---|
| Epley | weight × (1 + reps ÷ 30) | Most widely used; slightly high at higher reps |
| Brzycki | weight × 36 ÷ (37 − reps) | Accurate for low reps |
| Lombardi | weight × reps^0.10 | Gentler curve at higher reps |
Using the training-load table
Programmes often prescribe intensity as a percentage of 1RM. Heavy strength work is typically 80–90% for 3 to 6 reps, muscle-building work 65–80% for 8 to 12 reps, and technique or speed work lighter. The table lists the weight at each percentage and the reps most people can manage at that load, based on common strength-coaching tables. Individuals vary — some can do more reps at a given percentage, especially on lower-body lifts — so treat the reps as a guide and adjust by feel.
Getting a good estimate
Warm up well, then use a weight you can lift with good form for roughly 3 to 6 reps, stopping when the next rep would break down. Count only clean reps. Retest every few weeks as you get stronger. Estimates from very high-rep sets are less accurate because endurance starts to matter more than strength. Compare like with like: the estimate for one lift does not transfer to another.
Tracking progress
An estimated one-rep max is a convenient way to track strength over time without testing a true max. Record the weight and reps of your heaviest working set each week; if the estimate rises, you are getting stronger, even when the sets themselves look different. Because the formulas are consistent with each other, comparing estimates from the same formula and a similar number of reps gives the clearest trend. Many training apps and programmes use the same idea to adjust loads automatically from session to session.
Safety
Testing a true one-rep max is best left to experienced lifters with a spotter or safety bars, after a thorough warm-up. Beginners gain strength quickly by training with moderate weights and progressing steadily, and do not need to test maxes at all. Stop if you feel sharp pain. If you have heart disease, high blood pressure or a recent injury, ask a doctor before heavy lifting, which raises blood pressure sharply during the effort.
Frequently asked questions
How do I calculate my one rep max?
Enter a weight and the reps you completed; the calculator applies the Epley, Brzycki and Lombardi formulas and averages them.
Which 1RM formula is most accurate?
They are similar for 2–10 reps. The average of several formulas is a sensible estimate.
How many reps should I use for the estimate?
About 3 to 6 clean reps give the most reliable result.
Can I use pounds?
Yes. Choose lb; the formulas work the same in either unit.
What percentage of 1RM should I train at?
About 80–90% for strength, 65–80% for muscle growth.
Is my data stored?
No. The calculation runs in your browser.
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