Valeria Tools
One Rep Max Calculator
Find your estimated maximum strength for any lift — then use the training load table to build your entire program around it.
Three Formulas, One Accurate Result
- ✓The Epley formula (1985) is the most widely used and works best in the 1–10 rep range.
- ✓The Brzycki formula (1993) is more conservative and tends to be more accurate in the lower rep ranges (1–6).
- ✓The Mayhew formula (1992) was validated specifically on women and performs well across a wider rep range.
- ✓This calculator averages all three — reducing the error of any single formula and giving you a more reliable estimate.
How to Use Your 1RM in Training
- 1.For hypertrophy (muscle growth): train in the 70–80% zone — this corresponds to roughly 8–12 reps at a challenging weight.
- 2.For strength: periodically train in the 80–90% zone (4–6 reps) to build the neurological efficiency to handle heavy loads.
- 3.For metabolic work and pump: use 55–65% (15–20 reps) as finisher sets to maximize metabolic stress.
- 4.Progressive overload: when you can complete the top of your target rep range with good form, increase the weight by 2.5–5 kg and recalculate.
Frequently Asked Questions
How accurate are 1RM calculators?
Accuracy is best with 1–6 reps (within 5–8%). At higher rep counts (12+), accuracy decreases because fatigue factors vary more between individuals. For best results, use a weight you can lift 3–8 times to failure.
Should I actually test my 1RM?
For most women, calculating 1RM from a submaximal test (e.g., 5 reps near failure) is safer and nearly as accurate as an actual 1RM attempt. True 1RM testing requires significant warm-up, a spotter, and should not be done more than once every 8–12 weeks.
My numbers went up — when should I recalculate?
Recalculate every 4–8 weeks, or whenever you notice that your target weight for a given rep range is consistently feeling too easy. Your training loads should always feel challenging in the last 1–3 reps.
Why does the table round to 2.5 kg?
Most gym plates come in 2.5 kg increments. The table rounds to the nearest 2.5 kg to give you a practically loadable weight rather than a theoretical number.