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Good to Know
These formulas are estimates calibrated against sets of roughly 1-10 reps — they become increasingly unreliable at higher rep counts and do not account for lift type, technique, or individual variation. Always use a spotter and proper form when actually attempting a new one-rep max.
Disclaimer
This calculator provides estimates for informational purposes only and does not constitute financial, medical, legal, or tax advice. Always consult a qualified professional about your specific situation.
How This Calculator Works
A one-rep max (1RM) is the heaviest weight you could lift for a single repetition, estimated
from a lighter weight you’ve already lifted for multiple reps. Enter the weight lifted and how
many reps it took, and this calculator shows the estimate from three long-standing published
formulas, plus their average.
None of these formulas is more “correct” than the others — they’re each independently derived and
can disagree meaningfully, especially at higher rep counts, which is why all three are shown
rather than picking one as the answer.
The Formula
Every formula below uses the same two inputs — weight lifted and reps completed — so the
same two colors track the same two quantities across all three:
These formulas are calibrated against sets of roughly 1–10 reps — estimates at much higher rep
counts become increasingly unreliable, and Brzycki’s formula specifically becomes mathematically
invalid at 37 reps or more.
Worked Example
Lifting 200 lbs for 5 reps:
Epley: 200×(1+5÷30)≈233.3 lbs
Brzycki: 200×36÷(37−5)=225 lbs
Lombardi: 200×50.10≈234.9 lbs
Average: ≈231.1 lbs
Cómo funciona esta calculadora
El máximo de una repetición (1RM) es el peso más pesado que podrías levantar en una sola
repetición, estimado a partir de un peso más ligero que ya has levantado varias veces. Ingresa
el peso levantado y cuántas repeticiones tomó, y esta calculadora muestra la estimación de tres
fórmulas publicadas y ampliamente utilizadas desde hace tiempo, además de su promedio.
Ninguna de estas fórmulas es más “correcta” que las demás — cada una se derivó de forma
independiente y pueden discrepar de manera significativa, especialmente con conteos de
repeticiones más altos, razón por la cual se muestran las tres en lugar de elegir una sola como la
respuesta.
La fórmula
Cada una de las siguientes fórmulas usa las mismas dos variables de entrada — el peso
levantado y las repeticiones completadas — por lo que los mismos dos colores identifican las
mismas dos cantidades en las tres:
Estas fórmulas están calibradas para series de aproximadamente 1 a 10 repeticiones — las
estimaciones con conteos de repeticiones mucho más altos se vuelven cada vez menos confiables, y
la fórmula de Brzycki en particular se vuelve matemáticamente inválida a partir de 37 repeticiones.
Epley, Brzycki, and Lombardi are each independently derived from different sets of lifting data, so they weight the relationship between reps and weight slightly differently. None is universally more accurate — the differences tend to grow at higher rep counts.
How accurate is a calculated one-rep max?
These are estimates, not a substitute for an actual tested max — factors like technique, fatigue, and which specific lift you're doing all affect how well the estimate holds up. They're most reliable for sets of about 1-10 reps.
Should I actually attempt my calculated one-rep max?
Use these estimates for programming training percentages (e.g. "work at 80% of your 1RM"), not necessarily as a target to attempt outright — if you do want to test a real one-rep max, always use a spotter and proper warm-up.
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