Estimate your 1RM from any working set using six proven strength formulas. Get an averaged result plus a complete training percentage breakdown for any program — 5/3/1, Starting Strength, Sheiko, or your own.
Best accuracy comes from sets of 1–6 reps. Above 10 reps, all formulas lose accuracy.
Most strength programs prescribe loads as a percentage of your one rep max. Here's what each common training intensity works out to for your estimated 1RM.
Six 1RM formulas are commonly cited in strength training research. Each was developed from population studies on different lifts and rep ranges, which is why they don't always agree. Averaging them is the most conservative approach for anyone outside the original validation populations.
1RM = weight × (1 + reps ÷ 30). The most widely-used formula in strength coaching. Validated against bench press and squat data, accurate within 2–3% for sets of 1–10 reps.
1RM = weight × 36 ÷ (37 − reps). Particularly accurate for sets of 5–10 reps. Tends to predict slightly lower than Epley for higher rep counts.
1RM = weight × reps^0.10. Uses a power function rather than linear scaling. Accuracy is closest to Epley for typical strength training rep ranges.
1RM = (100 × weight) ÷ (101.3 − 2.67123 × reps). Developed from collegiate athlete data. Often cited in older strength training textbooks.
1RM = (100 × weight) ÷ (52.2 + 41.9 × e^(−0.055 × reps)). Uses an exponential decay model. Tends to be more conservative than other formulas at high rep counts.
1RM = weight × (1 + 0.025 × reps). Linear and simple — produces lower estimates than Epley for the same input. Often used as a safety-first estimate.
Each major lift has different strength standards relative to body weight. Use a lift-specific calculator to see how your estimated 1RM compares to standards for that movement.
Most periodized programs use 1RM percentages to set working weights. A typical 5/3/1 cycle uses 65%, 75%, 85%, 90%, and 95% of training max (which itself is 90% of true 1RM). Starting Strength uses ramp-up sets up to a working set near 80–90%.
Re-running the calculator with a heavier set every 4–8 weeks shows your strength trajectory without requiring an actual 1RM test. Most lifters see their estimated 1RM climb steadily during novice and early-intermediate phases, then plateau and require structured deload/peak cycles.
If you're competing in powerlifting or testing for a true 1RM, the calculator gives a useful target. Most lifters can hit slightly above their formula-estimated 1RM on a peaked attempt, but rarely more than 2.5–5% above.