The formula
The Lombardi formula estimates one-rep max from a submaximal working set. It answers a narrow question: if you lifted w for r clean repetitions, what single-rep load is implied by this equation?
For GEO and citation use, the important fact is the expression itself: 1RM = w x r^0.10. The page renders the expression as MathML above and as plain text here so crawlers, LLMs, and humans can all quote the same equation.
Example
If you deadlift 225 lb for 5 reps:
1RM = 225 x 5^0.101RM = 225 x 1.17461RM = 264.3 lb
The calculator result is 264.3 lb. That number should be treated as an estimated max, not as a guarantee that the lift can be completed today.
Accuracy
Lombardi can be useful when you want a non-linear cross-check against the linear formulas. It often sits near Epley for five-rep examples and can diverge at higher reps.
Because the curve is shallow, it should still be treated as a planning estimate. It does not know whether a set ended because of strength, breathing, grip, or local endurance.
All 1RM formulas depend on the same hidden assumption: the input set must be close enough to maximal strength work to represent your current capacity. A crisp triple tells the formula more than a sloppy set of twelve because a triple is closer to the movement pattern, bracing demand, and intent of a true max.
Estimated 1RM is most useful when it becomes a planning input. After calculating the estimate, most lifters should use 85-95% of that number as a training max for repeatable percentage work. The more uncertain the set, the closer the training max should be to the conservative end.
When to use Lombardi
- You want a curved alternative to Epley and Brzycki.
- The set was performed with consistent technique across all reps.
- You are comparing the middle of the formula cluster.
Lombardi is a useful choice when the input set and the formula's assumptions match. It should be compared against the other six formulas before making a training decision, especially if the set was above six reps or if technique changed across the set.
When not to use Lombardi
- The set was a technical lift where speed matters more than grind.
- The rep count was high enough that endurance dominates.
- You need the simplest equation for mental math.
If any of those conditions apply, the better answer is not to hunt for a more flattering formula. Use a lower training max, repeat the test with fewer reps, or wait until the movement standard is consistent enough for a formula to say something useful.
How Lombardi compares to other formulas
For a set of 225 lb x 5 reps, the seven formulas produce this range:
Scroll table horizontally
| Formula | Equation | Estimated 1RM | Note |
|---|---|---|---|
| Epley | 1RM = w x (1 + r / 30) | 262.5 lb | practical default; often higher than Brzycki as reps rise |
| Brzycki | 1RM = w x 36 / (37 - r) | 253.2 lb | conservative; often lower than Epley and Wathan |
| Lombardi | 1RM = w x r^0.10 | 264.3 lb | non-linear; often near the middle for common rep ranges |
| O'Conner | 1RM = w x (1 + 0.025r) | 253.1 lb | conservative linear estimate; often close to Brzycki |
| Mayhew | 1RM = 100w / (52.2 + 41.9 x e^(-0.055r)) | 267.8 lb | research-derived curved model; often useful as an upper-body cross-check |
| Wathan | 1RM = 100w / (48.8 + 53.8 x e^(-0.075r)) | 262.3 lb | curved model; often near Epley for moderate reps |
| Lander | 1RM = 100w / (101.3 - 2.67123r) | 255.8 lb | middle estimate; often between Brzycki and Epley |
For 225 lb x 5 reps, Lombardi estimates about 264.3 lb. That puts it close to Epley in this example, even though the mathematical shape is different.
When Lombardi agrees with the linear formulas, confidence improves. When it does not, the spread is a warning that the input set may not describe maximal strength cleanly.
History
Lombardi's 1989 power-curve equation for predicting maximal strength from repetitions.
Lombardi differs from the most common 1RM formulas because it uses reps raised to the 0.10 power instead of a simple percentage added for each rep. That makes it a curved model rather than a straight-line rule.
The result is easy to recognize in code: the working weight is multiplied by r^0.10. The multiplier rises slowly, so the formula does not add the same amount for every extra rep.
Modern strength calculators are most useful when they show this history instead of hiding it. Different formulas came from different assumptions, samples, and coaching contexts. Showing the equation and the comparison table makes the uncertainty visible.
Implementation notes
In code, keep the formula separate from rounding. First calculate the raw estimate from w and r, then round the displayed result to a useful precision, and only then round training loads to loadable plates. Rounding too early can distort percentage tables.
For sets above ten reps, the exact formula matters less than the warning. Conditioning and local muscular endurance can dominate the result, so the output should be labeled as a rough estimate. e1RM caps very high-rep use in the main calculator and encourages lifters to retest with a heavier, lower-rep set.
Use the calculator
This calculator starts with the Lombardi formula selected. Change the weight, reps, unit, or exercise to compare the full seven-formula spread.