1RM Calculator — Estimate Your One-Rep Max
Enter a weight and reps to get an Epley and Brzycki estimate of your 1RM. The same math runs inside NEONREP — log a working set in the app and PR detection compares against the exact same number.
Epley estimate
262.5lb
Brzycki estimate
253.1lb
No credit card. PR detection inside the app uses the same Epley estimate.
About the estimators
Epley: 1RM ≈ weight × (1 + reps / 30). Standard in most lifting apps. Slightly aggressive at low reps (e.g., 225×1 would estimate 232.4 lb — we special-case rep=1 to return the input weight). Accurate within ~5% for 2-10 rep range.
Brzycki: 1RM ≈ weight × 36 / (37 − reps). More accurate at very low reps (1-5). Undefined above 12 reps — our calculator shows no value there. Brzycki tends to read 3-5% lower than Epley at the same inputs, which makes it a useful conservative cross-check.
For a true 1RM, test it. For everything else — programming, PR tracking, load selection — estimators are enough. NEONREP's PR detector uses Epley by default; the in-app behavior matches what you see here.
Frequently asked
How accurate are 1RM estimators?+
Epley and Brzycki are within ~5% of a tested 1RM for most lifters in the 2-10 rep range. Above 10 reps, error grows fast — at 15+ reps the estimate is more "trend signal" than precise number. For your true 1RM, test it.
Epley vs Brzycki — which formula is better?+
Epley (weight × (1 + reps/30)) is the standard in most lifting apps. Brzycki (weight × 36 / (37 − reps)) is more accurate at low reps (1-5) but undefined above 12. Our calculator shows both side-by-side so you can compare.
Why does Epley give a higher number than Brzycki?+
At 5 reps Brzycki gives ~12.5% over the weight; Epley gives ~16.7%. Both are estimates — the "true" 1RM depends on how close you are to failure on the test set. If you grinded the last rep, Brzycki is closer; if you had 1-2 in reserve, Epley is closer.
Should I test my true 1RM?+
For competition lifters, yes — periodically. For everyone else, the estimator is enough. Testing 1RMs adds CNS fatigue and injury risk; estimating from your working sets gives you 95% of the data with 5% of the cost.
How does NEONREP use 1RM estimates?+
Every set you log feeds the Epley estimator. PR detection fires when a new estimate beats your previous best. The same formula runs here on the landing page — log a 225 × 5 set in the app and the PR-detection threshold is the same number you see here.
What about AMRAP / failure sets?+
AMRAP sets (as-many-reps-as-possible) feed the estimator the same way — if you hit 5 AMRAP at 225 lb, the estimator sees (225, 5). The estimator doesn't care if there were more reps left in the tank; it just sees the load × reps you logged.