Free strength calculator
One-rep max calculator
Estimate your one-rep max from weight and reps using Epley and Brzycki formulas, then see practical training percentages.
Reviewed March 26, 2026
Estimate from a completed set
Average estimate
212 lb
Epley
215.8 lb
Brzycki
208.1 lb
What this result means
Enter a challenging set of 2–12 reps to estimate your one-rep max. The calculator shows Epley, Brzycki, and an average estimate plus a percentage-based loading table. It is an estimate—not a measured maximum.
Epley: 1RM = weight × (1 + reps ÷ 30). Brzycki: 1RM = weight × 36 ÷ (37 − reps).
How to use an estimated 1RM
Use the result to compare the same exercise across time, choose approximate percentage-based loads, or avoid frequent maximal testing. A rising estimate from comparable hard sets can indicate improving strength.
Treat the number as a range. Formulas respond differently to rep count, exercise, technique, and individual endurance.
Choose a useful input set
Use a recent set with stable technique and high effort. Sets above roughly twelve reps make common formulas more sensitive to individual muscular endurance.
Do not perform an unsafe set to failure just to improve the calculator. A hard submaximal set is sufficient for trend tracking.
Frequently asked questions
How accurate is a one-rep max calculator?
It provides an estimate. Accuracy varies by formula, exercise, rep range, technique, and the effort of the input set.
Which 1RM formula is best?
There is no universally best formula. Epley and Brzycki are common; consistency with one method is valuable for tracking trends.
Can beginners use estimated 1RM?
Yes, but beginners should prioritize technique and avoid unnecessary maximal testing.
Sources and assumptions
Put the estimate in context
Let your coach follow estimated strength over time.
LogFast uses your approved sets, reps, load, and effort to calculate comparable strength trends and help reason about a sensible next exposure.
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