Not medical advice.These estimates are for general informational use only and aren't a substitute for professional medical advice, diagnosis, or treatment. Consult a qualified healthcare provider before changing your diet, exercise, or medication.

What is a one-rep max?

Your one-rep max (1RM) is the most weight you can lift for a single repetition of an exercise. Rather than testing it directly (which is fatiguing and riskier), this calculatorestimates it from a set you've already done — a weight and the number of reps — using established prediction equations.

The formulas

For a load w lifted for r reps, calivue computes three well-known estimators:

Epley: 1RM = w × (1 + r / 30)
Brzycki: 1RM = w × 36 / (37 − r)
Lombardi: 1RM = w × r^0.1

Sources: Epley B., Poundage Chart (Boyd Epley Workout, Lincoln NE, 1985); Brzycki M., "Strength testing — predicting a one-rep max from reps-to-fatigue," JOPERD 64(1), 1993; Lombardi V.P., Beginning Weight Training (Wm. C. Brown, 1989).

We show each result plus their average, which smooths out the quirks of any single formula. The training-percentage table is built from that average using the Epley relationship between intensity and reps.

Accuracy & safe testing

These equations are most accurate at low rep counts (about 1–10); the more reps you do, the more fatigue, technique and conditioning skew the estimate, so we cap input at 30 reps. Treat the number as a training guide, not a guarantee. If you ever test a true 1RM, warm up thoroughly, use good form, and have a spotter or safety bars.

These estimates are for general training information only and are not medical or coaching advice.

Frequently asked questions

Which formula should I trust?

For most people the three land within a few percent of each other, so the averageis a sensible default. Brzycki tends to read a little lower at higher reps and Epley a little higher — at 1–5 reps they're very close.

How many reps give the best estimate?

Sets of 2–5 reps give the most reliable 1RM estimate. Above ~10 reps the numbers get progressively less trustworthy because endurance and fatigue dominate.

What is the percentage table for?

It converts your estimated 1RM into working loads — e.g. 80% for sets of about 8 — so you can program your sessions. The "~reps" column is a rough guide to how many reps each percentage typically allows.

Is my training log saved or sent anywhere?

No. When you add a lift to the log, it's stored only in this browser so the chart remembers your progress on your next visit. Nothing is uploaded to a server and no account is required — clearing your browser data removes it.