About 1RM Calculators

Most percentage based programs assume you already know your max, but they rarely tell you how to find it or how far to trust it. Two calculators can return different answers for the same set, and nobody explains why. This site exists to close that gap. Every tool shows its method, its valid range and its margin of error, so you can see how reliable a number is before you put it on the bar. No max-day test is needed, and nothing is hidden behind a single “magic” output. Please read our 1RM Calculator Disclaimer to understand the limitations of our calculator results and how to use them responsibly.

Why He Built This Tool

The calculators I found either ran one formula without saying which, buried the result under ads, or stopped at a single number. None showed how far the formulas disagreed, so there was no way to judge how reliable the estimate was. I built this site so that the answer, the spread around it and the reason for it sit on one screen.

What You’ll Find Here

The Calculator

  • All-Formulas 1RM Calculator: enter a weight and reps, and see seven formulas (Epley, Brzycki, Lander, Lombardi, Mayhew, O’Conner and Wathan) side by side with a dot-plot of the spread, reliability flags for each formula, and exercise-specific recommendations.
  • RPE Calculator: works in three modes. Find Weight gives you the load for a target RPE and reps, Estimate 1RM turns a finished set into an e1RM, and Plan Sets lays out a full session with fatigue built in. It uses the RTS percentage chart (RPE 6–10, 1–12 reps).
  • Wilks Score Calculator: returns Wilks (1998), Wilks 2020 and DOTS from the same inputs, accepts kilograms or pounds, and shows a personalized strength-standards table for your bodyweight.

All three run inside your browser. The numbers you type are never uploaded, and each tool can export or print your results as a PDF.

The Guides

The guides cover what a calculator cannot: what a one-rep max really means, why the formulas disagree, how to retest and how often, how to use a Training Max, how RPE differs from RIR, and how to read Wilks and DOTS without being misled. They are written for lifters who want the reasoning behind the number, not just a template.

Editorial Standards

  • Formula authors and years are named correctly (for example Epley 1985, Brzycki 1993, Wilks 2020).
  • Where evidence is mixed, we say so. We do not invent studies, quotes or client stories.
  • Every formula’s limits are stated: the rep range where it holds up and where it starts to guess.
  • Corrections are applied after checking and noted on the page. Pages carry a “last reviewed” date.
  • Results are estimates, not guarantees. See the Disclaimer for the full accuracy and liability position.

Who This Site Is For

Lifters who already train and want to train more intelligently: intermediate lifters running percentage or RPE programs, powerlifters tracking meet readiness, coaches who need a shared language for load and effort, and anyone comparing strength across bodyweights. If you want motivation posts or beginner workout plans, this is not the right place. If you want to understand your numbers and use them properly, it is.

Get in Touch

Use the contact form for calculator bugs, content corrections or topic suggestions. It is not a coaching service. Messages are usually answered within [2] business days.