About One Rep Max Calculators

Why This Site Exists

Most percentage-based programs assume you already know your 1RM. They don’t tell you how to find it, how reliable the number is, or what to do when the calculator you used gives a different result from the one your training partner used. This site exists to close that gap. The calculator takes the weight and reps from a set you’ve already done and returns a working 1RM estimate across seven established formulas, alongside a full percentage table and warm-up ramp. No max-day test required. No guesswork on what to put on the bar Tuesday.

Who Is Behind It

Michael Swan

I’ve been training with barbells for 15 years, working through programs and paying close attention to how percentage-based loading actually behaves across training cycles. My background is practical: I’ve trained in commercial gyms and home setups, tested true maxes and estimated them, and spent a lot of time understanding why the calculator number and the bar number don’t always agree.

I’m not a researcher or an academic. I don’t have a sports science degree. What I have is years of working through the same problems every serious lifter runs into when they try to program intelligently off a number they’re not entirely sure is accurate.

Why He Built This Tool

The existing 1RM calculators I found were either cluttered with ads and popups, running a single formula with no explanation of which one, or built by people who clearly hadn’t thought about how a lifter actually uses the output. Most gave you a number and stopped there. None showed you the spread across formulas, so you had no way to gauge how reliable the estimate was. None connected the estimate to a training percentage table in a way that was actually useful.

I built this one to do all of that in one place: seven formulas running simultaneously, a percentage and rep-max table that updates from your input, a warm-up ramp, and an RPE reference. And I wrote the guides to explain the parts that calculators don’t, because knowing your 1RM is only useful if you know what to do with it.

What You’ll Find Here

The Calculator

The one rep max calculator on the homepage takes three inputs: the lift, the weight you used, and the reps you completed. It returns your estimated 1RM across seven formulas (Epley, Brzycki, Lander, Lombardi, Mayhew, O’Conner, and Wathan) at once. Below that, a percentage and rep-max table shows your target weights from 50% to 100% of the estimate. A warm-up ramp and RPE reference are also built into the same page. The lift selector applies the right formula default for each movement automatically.

The Guides

The guides section covers the topics a calculator can’t: what a 1RM actually means, how each formula was developed and where it breaks down, how to test safely, how to read strength standards relative to your bodyweight, and how to build a program around the number you have. The guides are organized by topic and written for lifters who want to understand the reasoning, not just copy a template.

Editorial Standards

Articles on this site cite real formula authors with publication years, name specific programs correctly, and draw on published research from sources including the NSCA and ACSM. When evidence is mixed or unsettled, that’s stated directly rather than smoothed over. No studies are invented. No anecdotes are fabricated. When a formula has a known limitation, we say so and explain why.

For the full accuracy policy and liability position, see the Disclaimer.

Who This Site Is For

This site is built for lifters who already train and want to train more intelligently. Intermediate lifters running percentage-based programs. Powerlifters tracking competition lifts. CrossFitters managing loading across multiple movements. Coaches who need a quick reference for athletes. If you’re looking for motivational content or beginner workout plans, this isn’t the right place. If you want to understand your numbers and use them properly, it is.

Get in Touch

Use the contact form for feedback on the calculator, corrections to guide content, or suggestions for topics we haven’t covered. The contact form is not a coaching inquiry service. Response time is typically within two business days.