Estimate your one-rep max (1RM) using 5 validated formulas (Epley, Brzycki, Lombardi, O'Conner, Wathan). Shows an averaged result, full training percentage table (50–100% of 1RM), and a plate calculator for your gym setup.
Enter the weight you lifted and the number of reps you completed. Most accurate for 1–10 reps with strict form. Avoid grinding or failed reps — the estimate assumes clean, controlled repetitions at or near maximum effort.
Five formulas (Epley, Brzycki, Lombardi, O'Conner, Wathan) each calculate a 1RM estimate. The averaged result is shown prominently. Individual formula results let you see the range.
A table shows training weights at 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95% of your estimated 1RM — the foundation of percentage-based programming for strength, hypertrophy, and power.
Your one-rep max (1RM) is the maximum weight you can lift for exactly one complete repetition with proper form. It is the gold standard measure of muscular strength in strength sports (powerlifting, weightlifting). Knowing your 1RM allows percentage-based training programming — prescribing work sets at specific percentages of your max to target different adaptations.
Epley (1985) and Brzycki (1993) are the most widely validated formulas. Epley tends to be slightly more accurate for lower rep counts (1–6 reps); Brzycki is slightly better for higher rep counts (7–10 reps). The averaged result from multiple formulas generally outperforms any single formula. All formulas become less reliable above 10 repetitions.
Percentage-based programming uses your 1RM to prescribe training intensity: 85–100% develops maximal strength (1–3 reps), 75–85% builds strength-hypertrophy (4–6 reps), 65–75% develops hypertrophy (8–12 reps), 50–65% builds muscular endurance (15+ reps). Without knowing your 1RM, you cannot accurately apply these programming percentages.
Actual 1RM testing carries injury risk, especially for beginners or without a spotter. This calculator estimates 1RM from a submaximal set (85–90% effort at 3–6 reps) which is safer and often sufficiently accurate for programming purposes. If testing an actual 1RM, warm up thoroughly, use a spotter, and only attempt exercises you have mastered. Never test 1RM to complete failure.
Re-estimate your 1RM every 4–6 weeks as your strength progresses. In practice, this happens naturally when you track your lifts — as you lift heavier weights for the same reps, your estimated 1RM increases. Formal 1RM testing (actual or estimated) is typically done at the end of training blocks (8–12 week mesocycles) to measure progress and set new training percentages.
The calculator works for any barbell or machine exercise: squat, bench press, deadlift, overhead press, bent-over row, hip thrust, leg press, lat pulldown, and cable exercises. The formulas are valid regardless of exercise — they estimate 1RM from any weight-reps combination. Note that 1RM estimates are less reliable for exercises where technique breaks down under heavy load.
