Free 1RM calculator
One-rep max calculator: Epley 1RM estimate with confidence
Estimate your one-rep max from weight and reps using the Epley formula. See the exact calculation, rep-range confidence, examples, and practical limits.
Enter a completed working set. The calculator uses the Epley equation: e1RM = weight × (1 + reps ÷ 30). A true single returns the weight itself. Results from lower-rep sets usually deserve more confidence than results from long sets.
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Estimate your one-rep max
Estimated one-rep max
263 lb
Strong estimate range: 1–5 reps
225 × (1 + 5 ÷ 30) = 262.5 lb
How the Epley 1RM formula works
The formula converts a submaximal set into the load you might lift for one repetition. For 225 lb × 5 reps:
225 × (1 + 5 ÷ 30) = 262.5 lb estimated 1RMThat does not mean 262.5 lb is guaranteed on the platform tomorrow. It is an estimate based on a general relationship between reps and load. Skill, exercise selection, fatigue resistance, technique, and how close the set was to failure all change the relationship.
How much should you trust the estimate?
| Reps in the set | Practical interpretation |
|---|---|
| 1 | The performed load is the one-rep result |
| 2–5 | Strongest range for comparing strength-oriented work |
| 6–10 | Useful for trend tracking; less exact as a max prediction |
| 11–15 | Rough index; individual fatigue resistance matters much more |
| 16+ | Too indirect for a confident max estimate |
The confidence note is a practical guardrail, not a probability. If you consistently use the same exercise, technique, and rep range, the trend is often more useful than the absolute number.
Best uses for estimated 1RM
- Compare a 5-rep personal best with a previous 3-rep set.
- Track a lift’s strength trend without frequent maximal testing.
- Notice sustained performance decline during a difficult training block.
- Provide context for percentage-based planning when a tested max is stale.
Estimated 1RM is not a permission slip to attempt the number. A maximal lift is a separate skill and carries a different fatigue and risk profile. The complete estimated 1RM methodologyexplains how Flexbound uses the number and where it deliberately does not.
Epley versus Brzycki and other formulas
Epley, Brzycki, Lombardi, and related equations often produce similar answers in moderate rep ranges and diverge as reps rise. No single formula is universally correct for every lift and lifter. Flexbound uses Epley because it is simple, widely recognized, easy to audit, and suitable for tracking consistent trends. Using one formula consistently is usually more informative than switching formulas to find the preferred answer.
Frequently asked questions
Should warm-up sets go into a 1RM calculator?
No. Use a challenging, technically valid working set. A warm-up set stops because the plan says stop, not because it reveals your current capacity.
Does the set need to reach failure?
The closer the set is to your actual rep capacity, the more informative it is for max estimation. That does not mean every set should reach failure. Record RIR or RPE so you remember how much capacity remained.
Can I use this for dumbbells?
Yes, but decide whether the entered weight represents one dumbbell or the combined pair, then stay consistent. Compare like with like.