Two formulas, one honest range
Epley (weight × (1 + reps/30)) and Brzycki (weight × 36 ÷ (37 − reps)) are the two most used 1RM estimators. For a true single both return the bar weight itself; through the middle ranges Epley reads a few percent higher (about 9 lb on a 225 lb set), the two meet again at exactly 10 reps, and past 10 the order flips — Brzycki reads higher. Showing both gives you a working range instead of a false-precision single number — but both are population formulas, and studies find lifters whose tested max falls outside the pair, so treat the range as a planning start, not a guarantee. Estimates from 10 reps or fewer are the most trustworthy, which is why the input stops at 12.
Using the percentage table
Strength programs speak in %1RM. As a rough map: 85–95% for low-rep maximal strength, 70–85% for classic 5–8 rep work, 60–70% for volume and technique days. The table above multiplies your estimated max through those percentages, so a program that says "5×5 at 75%" becomes an actual number on the bar.
Estimate, don't grind
The entire point of estimating is skipping risky max attempts. If you do test a true single: full warm-up, small jumps, a spotter or safety pins, and stop the moment form breaks. And the standing caveat — these are training estimates from population formulas, not medical or coaching advice; your leverages, fatigue and lift choice all move the number.
FAQ
225 × 5 = what max?
≈ 262 lb (Epley) / 253 lb (Brzycki).
The formulas?
Epley: w × (1 + r/30), a 1-rep single counting as the weight itself. Brzycki: w × 36 ÷ (37 − r).
Which is right?
Neither consistently — Epley higher below 10 reps, equal at 10, Brzycki higher past 10. Treat the pair as a planning range; your tested max can sit outside it.
Safe to test?
Estimate instead; if testing — warm-up, spotter, no grinding.
%1RM use?
Programs prescribe loads by it; the table turns % into bar weight.