ZOVATOOL

One Rep Max Calculator

Estimated 1RM (avg of 7 formulas)
115.5 kg
Epley
116.7 kg
Brzycki
112.5 kg
Lander
113.7 kg
Lombardi
117.5 kg
Mayhew
119.0 kg
O'Conner
112.5 kg
Wathan
116.6 kg
% of 1RM training table (using avg 1RM)
1 reps · 100%115.5 kg
2 reps · 95%109.7 kg
3 reps · 93%107.4 kg
4 reps · 90%103.9 kg
5 reps · 87%100.5 kg
6 reps · 85%98.2 kg
7 reps · 83%95.9 kg
8 reps · 80%92.4 kg
9 reps · 77%88.9 kg
10 reps · 75%86.6 kg
12 reps · 70%80.8 kg
15 reps · 65%75.1 kg
20 reps · 60%69.3 kg
Formulas (w=weight, r=reps)
Epley: w × (1 + r/30)
Brzycki: w × 36 / (37 − r)
Lander: 100w / (101.3 − 2.67123 r)
Lombardi: w × r^0.10
Mayhew: 100w / (52.2 + 41.9 e^(−0.055 r))
O'Conner: w × (1 + 0.025 r)
Wathan: 100w / (48.8 + 53.8 e^(−0.075 r))

How to use the 1RM Calculator

  1. Enter the weight lifted and the number of clean reps completed (RIR = 0).
  2. Select formula — Epley (default, accurate to 10 reps), Brzycki (best under 6 reps), Lombardi, Wathan, Mayhew or O'Conner.
  3. Read estimated 1RM across all formulas — spread of 5–10% is normal.
  4. Read percentage training loads: 50%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95% of 1RM.
  5. Choose a training block: hypertrophy (65–80%), strength (85–95%), power (30–60% explosive), endurance (50–65% high-rep).
  6. Never estimate 1RM from sets over 10 reps — accuracy collapses.
  7. Retest with a 3–5 rep max every 4–8 weeks; update all program percentages.
  8. For safety: use spotters or safety bars when testing near max.
  9. Track 1RM over time to spot plateaus and drive periodization.
  10. Export percentage tables to build training programs.
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The 1RM calculator: how percentage-based training actually works

One Rep Max (1RM) is the maximum weight you can lift once with proper form. Every serious strength program — 5/3/1, Sheiko, Westside, Starting Strength, StrongLifts — expresses working weights as a percentage of 1RM. Nail the 1RM and every prescribed set becomes precise. Guess it and you're either grinding submaximal weights or attempting fantasy loads.

Formulas convert submaximal sets into 1RM estimates. Epley (1985): 1RM = weight × (1 + reps/30). Brzycki (1993): 1RM = weight × 36 / (37 − reps). Both are accurate up to 10 reps within ±5%. Beyond 10 reps, accuracy collapses because rep-max relationships are nonlinear — a 20-rep set is closer to a cardio challenge than a strength test. Never estimate 1RM from high-rep sets.

Training percentages map to specific adaptations. 30–60% of 1RM moved with maximum bar speed builds power (Olympic lifts, jumps, sprinter accessories). 65–80% for 6–12 reps drives hypertrophy — the classical bodybuilding zone. 85–95% for 1–5 reps builds absolute strength via neural adaptations. Over 95% is contest-day territory; too taxing for repeated training use.

The RIR concept — Reps In Reserve — bridges 1RM estimates and real training. A set is 'to failure' (RIR 0), 'one rep left in the tank' (RIR 1), or 'form breakdown imminent' (RIR 2). Programs like RPE-based training (Rate of Perceived Exertion) use RIR to self-regulate loads instead of fixed percentages. Both methods work; percentage-based is more prescriptive, RPE-based is more auto-regulated.

Testing versus estimating: elite lifters test true 1RM two to four times per year, typically in a peaking phase before a competition. Recreational lifters can safely estimate from 3–5 rep maxes every 4–8 weeks and update program percentages accordingly. Testing carries injury risk and CNS fatigue that costs 1–2 weeks of hard training after. The calculator's estimates are the safer default for 95% of trainees — accurate enough to program from, safe enough to check monthly.