Health & Medicine · Fitness · Strength Training
Lombardi One Rep Max Calculator
Estimates your one-repetition maximum (1RM) using the Lombardi formula based on weight lifted and repetitions performed.
Calculator
Formula
1RM is the estimated one-repetition maximum. w is the weight lifted (in any consistent unit, e.g. kg or lb). r is the number of repetitions completed. The exponent 0.10 is the Lombardi constant.
Source: Lombardi, V.P. (1989). Beginning Weight Training. Wm. C. Brown Publishers.
How it works
The Lombardi formula is expressed as 1RM = w × r0.10, where w is the weight lifted and r is the number of repetitions completed in a single set taken close to failure. The exponent 0.10 is the empirically derived Lombardi constant, making this one of the simpler 1RM prediction equations while remaining reasonably accurate in the low-to-moderate rep range.
The formula was introduced by V.P. Lombardi in the 1989 textbook Beginning Weight Training. Compared to other 1RM equations such as Epley or Brzycki, the Lombardi formula tends to produce slightly higher estimates, particularly at higher repetition counts, and is most accurate when reps performed fall between 2 and 10.
Training percentages derived from the estimated 1RM are essential for structured programming. Lifting at 85–95% develops maximal strength, 75–85% builds hypertrophy with moderate load, and 60–75% is used for technique work and muscular endurance. This calculator outputs five common training zones alongside the 1RM estimate.
Worked example
Example: A lifter performs a set of bench press with 100 kg for 8 repetitions.
Step 1: Identify inputs — w = 100 kg, r = 8 reps.
Step 2: Apply the Lombardi formula: 1RM = 100 × 80.10
Step 3: Calculate 80.10 = e0.10 × ln(8) = e0.10 × 2.0794 = e0.20794 ≈ 1.2311
Step 4: 1RM = 100 × 1.2311 ≈ 123.1 kg
Training zones: 90% = 110.8 kg | 85% = 104.6 kg | 80% = 98.5 kg | 75% = 92.3 kg
Limitations & notes
The Lombardi formula, like all 1RM prediction equations, is an estimate and not a substitute for a properly supervised maximal lift. Accuracy decreases significantly when the number of repetitions exceeds 10–12, as fatigue and technique breakdown introduce increasing error. The formula assumes each set is taken to or very near muscular failure; sets left well short of failure will produce underestimates. Individual factors such as fiber type composition, training age, lift technique, and exercise selection all affect how well the formula generalises. It should not be used for clinical or competitive purposes where an exact 1RM is required.
Frequently asked questions
What is the Lombardi formula for 1RM?
The Lombardi formula is 1RM = w × r^0.10, where w is the weight lifted and r is the number of repetitions completed. It was published by V.P. Lombardi in the 1989 textbook Beginning Weight Training.
How accurate is the Lombardi 1RM estimate?
The Lombardi formula is most accurate when the number of repetitions is between 2 and 10 and the set is taken close to failure. Beyond 10 reps, fatigue and muscle endurance factors cause the formula to overestimate the true 1RM. Studies comparing 1RM equations generally find mean errors of 2–5% within the 2–10 rep range.
How does the Lombardi formula compare to Epley or Brzycki?
All three are linear or near-linear 1RM prediction models. The Lombardi formula (w × r^0.10) tends to produce slightly higher estimates than Epley (w × (1 + r/30)) and Brzycki (w × 36/(37 − r)) at moderate rep counts. Brzycki is undefined above 36 reps, while Lombardi and Epley remain mathematically valid but increasingly inaccurate at high rep counts.
Should I use kilograms or pounds?
The Lombardi formula works with any consistent unit of weight. If you enter your weight in kilograms, the estimated 1RM and training percentages will be in kilograms. If you enter pounds, all outputs will be in pounds. There is no unit conversion built into the formula itself.
What rep range gives the best 1RM prediction?
The most reliable predictions come from sets of 2 to 6 repetitions taken to failure, as these are biomechanically closest to a true 1RM effort. Sets of 7 to 10 reps are still reasonably accurate. Beyond 10 repetitions, muscular endurance becomes a larger factor and the formula's accuracy declines noticeably.
Can I use this for any exercise?
Yes, the Lombardi formula can be applied to any barbell, dumbbell, or machine exercise where the weight and reps are measurable. However, prediction accuracy can vary by exercise. Compound movements like squat, bench press, and deadlift tend to yield more consistent estimates than isolation exercises, where stabiliser fatigue may cause you to stop before primary muscle failure.
What training weight should I use for hypertrophy?
Most evidence-based hypertrophy programming prescribes loads of 65–85% of 1RM, corresponding roughly to sets of 6–15 repetitions taken near failure. Use the 75–85% outputs from this calculator as a starting point for hypertrophy-focused training blocks.
Last updated: 2025-01-30 · Formula verified against primary sources.