About Us

Last updated: October 20, 2026

1 Rep Max Calculator is a free set of strength tools for people who lift. Enter one hard set and you get an estimated max, training weights, warm-ups and plate loading in a few seconds. No account, no email, no paywall.

Why this site exists

Most lifters want the same thing from a max calculator: a trustworthy number, quickly, on a phone between sets. Many tools online are slow, covered in pop-ups, or give a single figure with no hint of how it was worked out.

We built this site to fix that. Every page loads fast, works the same on a phone or a laptop, and shows its working. If you want to see how your estimate was reached, the formulas and the spread between them are one tap away.

Our team

1 Rep Max Calculator is built and run by a small team of developers and strength-training enthusiasts. We train ourselves, and we build the tools we wanted to use in our own sessions: free, fast and accurate, with nothing to sign up for.

Our team designs and codes the calculators, writes and edits the guides, and handles every update and correction. We are an independent project. We are not a gym, a coaching service or a medical provider, and we do not claim to be. The tools are here to help you plan your training with better numbers, not to replace a doctor or a qualified coach.

How our calculators work

A one rep max calculator predicts the heaviest single you could lift from a set of several reps. There is no single perfect equation for this, so we use seven well-known published formulas:

• Epley and Brzycki, the two most widely used
• Lombardi and O’Conner, two simpler models that tend to run high and low
• Wathen, Mayhew and Lander, built from research on trained lifters

The calculator runs all seven on your set and shows the median, the middle value. Using the median means one formula that runs unusually high or low cannot drag your result around. You can still switch to any single formula in Coach mode.

Want the details? See the 7 formulas explained, with the equation and a worked example for each one.

Our editorial standards

Every guide on this site is researched, written and then reviewed against the calculator before it goes live. We follow a few simple rules:

• Researched first. Explanations are based on the published formulas and on research into rep-max prediction, and we link to sources where it helps.
• Plain English. We explain terms like RPE and training max the first time they appear.
• Checked numbers. Every worked example is run through the same code the calculator uses, so the text and the tool always agree.
• Honest limits. We say when an estimate is less reliable, for example with very high reps or Olympic lifts.
• Regular reviews. Pages are reviewed and updated as we add features or find better ways to explain things. The date at the top of each page shows the last update.

Corrections

If you spot a mistake, a broken link or a number that looks wrong, please tell us through the Contact page and choose “Report an error”. We read every report and fix confirmed errors as quickly as we can.

Our calculators