What is a one-rep max (1RM)?

Your one-rep max is the heaviest weight you can lift for a single clean repetition of an exercise. It is the standard reference point for programming strength training — most programs prescribe working loads as a percentage of 1RM.

How does a 1RM calculator work?

It estimates your one-rep max from a set you have actually completed — a weight and a rep count. This calculator averages two validated formulas, Epley (weight x (1 + reps/30)) and Brzycki (weight x 36 / (37 - reps)), then builds a table of training loads at common rep targets as a percentage of the estimate.

How accurate is a 1RM estimate?

Most accurate when the input set is in the 1-6 rep range. Accuracy drops as reps climb, because higher-rep sets depend more on conditioning and rep endurance than on pure strength. Treat the number as a close estimate, not a tested max, and re-estimate from a fresh hard set every few weeks.

Should I test my actual one-rep max?

For most men 25-40 training for body composition, no. A true 1RM test carries injury risk and a recovery cost with little practical benefit. An estimate from a hard set of 3-6 reps is enough to program from. Competitive powerlifters test their max; general lifters are better off estimating.

How do I use my 1RM for training?

Use the percentage table. Strength work generally sits around 85-95% of 1RM for low reps; muscle-building work sits around 70-80% for moderate reps. Pick the weight next to your target rep count, then adjust based on how the set actually feels — the estimate gets you close, the set tells you the rest.

Free tool

1RM calculator

Estimate your one-rep max from any set using the Epley and Brzycki formulas, and get a training-load table for every rep target. No signup. No email gate.

How it works

The calculator takes a set you have actually done and runs it through two validated estimators — Epley (weight × (1 + reps/30)) and Brzycki (weight × 36 ÷ (37 − reps)) — then averages them. From that 1RM it builds a table of training loads at standard percentages.

It is an estimate, most accurate from low-rep sets (1-6). Use it to set programming loads and to track strength over time — re-run it from a fresh hard set every few weeks rather than testing a true max.

Want a coach to program the loads for you?

A 1RM is just a number. The work is turning it into a week of training that progresses — knowing when to add load, when to hold, and when to back off. That is what 1:1 coaching with Kris is for.

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