Estimated 1RM: the Epley formula and its limits

The formula, exactly as the app runs it

Every estimated one-rep max in Flexbound comes from theEpley equation:

e1RM = weight × (1 + reps ÷ 30)

A set of 225 × 5 estimates to 225 × (1 + 5/30) ≈ 262. A single at 315 is just 315. For 1-rep sets the formula returns the weight itself. That's the whole computation. There is no machine-learning model, no adjustment factor, no AI involvement.

Why Epley

Rep-max conversion charts of this family (Epley, Brzycki, and relatives) are standard tools in strength and conditioning practice, and at moderate rep counts they agree closely. We chose Epley because it's simple, widely understood, and errs slightly conservative in the ranges where lifters actually train. One documented formula beats a "smart" black box you can't check.

Where the estimate is trustworthy, and where it isn't

All rep-max formulas degrade as reps climb. Fatigue resistance varies between people and between lifts, so a 12-rep set says much less about your true single than a 3-rep set does.

What e1RM is for in Flexbound

• Trend lines on a lift's page show whether the estimate is drifting up over weeks
• Best-set context compares a 5-rep PR against a 3-rep PR fairly
• Deload detection uses sustained e1RM decline on a key lift as one input

What it's not for: telling you to attempt a max. An estimate is a map, not a permission slip. Test heavy singles deliberately and rested, if testing matters to your goals.