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One-Rep Max (Lombardi) Calculator

Enter the weight lifted and reps performed to estimate your one-rep max (Lombardi).

How it is calculated

The estimate is 1RM = W × R0.10, where W is the weight lifted and R is the number of repetitions completed in the set. The result comes out in whatever unit you typed for W (kg or lb); the tool does not convert. Weight must be above zero and reps must be at least 1, otherwise there is no result. Because the exponent is 0.10, a single rep returns the weight itself, and each extra rep adds only a small increment. The answer is rounded to two decimals. It is an estimate for a set taken close to failure, not a tested maximum.

Worked example

You lift 80 kg for 8 reps. Step 1: 80.10 ≈ 1.2311. Step 2: 80 × 1.2311 ≈ 98.49. The estimated one-rep max is 98.49 kg. A training percentage can then be taken from it, for example 80% of 98.49 is about 78.8 kg.

Try this example →

Common mistakes

  • Entering a set stopped well short of failure; the formula assumes the reps were hard, so an easy set of 8 underestimates your max.
  • Typing the total of several sets as the rep count; use the reps from one set only.
  • Mixing units, such as a pound weight read as kilograms, then loading the result on a kg bar.
  • Trusting the figure from a set of 20 or 30 reps; estimates become less reliable at high reps, and the tool will still give a number.

About this calculator

The Lombardi formula estimates one-repetition maximum (1RM) strength from a submaximal set using 1RM = weight × reps^0.10 — a power-law relationship rather than the linear ones used by formulas like Epley or Brzycki. Because the exponent is small, the estimate rises slowly with rep count, making Lombardi comparatively conservative at higher rep ranges.

Strength coaches and lifters use 1RM estimates like this to set training percentages (e.g., 80% of 1RM for a hypertrophy block) without the fatigue and injury risk of testing an actual single-rep max. Since no formula is exact, it works best on sets of roughly 10 reps or fewer.

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Comments (1)

  • Editorial team

    A handy sanity check: because the exponent is only 0.10, doubling the reps multiplies the estimate by about 1.07. So the same weight for 10 reps should land roughly 7% above the figure for 5 reps. If your own sets at different rep counts disagree with that by a wide margin, this formula may not suit your lift. Which exercise do you use it for, and how close does the estimate come to a heavy single?

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