One Rep Max Calculator
Estimate your 1RM using five validated formulas. Enter any weight and rep count from a recent set — the calculator cross-references Epley, Brzycki, Lombardi, Mayhew, and Wathan to give you a reliable range.
Your Set
Most accurate between 2–10 reps
What is a one-rep max and why does it matter?
Your one-rep max (1RM) is the heaviest weight you can lift for a single repetition with proper form. It is the foundation of percentage-based training — every serious strength program prescribes loads as a percentage of your 1RM. Knowing your max lets you train with precision: heavy enough to drive adaptation, light enough to recover. Without it, you are guessing.
How accurate are 1RM calculator formulas?
The five formulas used in this calculator — Epley, Brzycki, Lombardi, Mayhew, and Wathan — are each accurate within 5–10% when the input set falls between 2 and 10 reps. Accuracy drops noticeably above 10 reps because the relationship between submaximal weight and true max becomes less linear. This calculator averages all five formulas and shows you the range, giving a more reliable estimate than any single equation alone.
Should lifters over 40 test a true one-rep max?
For most lifters over 40, estimating your 1RM from a solid 3–5 rep set is smarter than grinding out a true max attempt. Connective tissue — tendons, ligaments, joint capsules — recovers more slowly with age, and true singles place disproportionate stress on those structures. A calculated 1RM gives you the training percentages you need to program effectively without the injury risk that comes with maxing out.
How to use your estimated 1RM for training
Use the percentage chart above to program your working sets. Strength work typically lives at 80–90% of your 1RM for sets of 3–6 reps. Hypertrophy training sits around 65–80% for sets of 8–12. Speed and power work uses 50–65% with explosive intent. A peaking program progressively increases intensity week over week, starting around 75% and building toward a new max attempt — this is exactly what a structured peaking cycle is designed to do.