One Rep Max Calculator
Nobody should test a true 1RM every week - it beats up the joints and stalls the program - so lifters estimate it from heavy sets instead. Enter the weight and reps you actually moved, and this calculator runs the three standard formulas at once: Epley (the classic, generous at high reps), Brzycki (accurate under 10 reps), and Lander, then averages them into the working number your percentages come from.
Alongside the max you get the practical translation: the 80% weight for 5x5 strength blocks, and the note reminds you where the estimates live honestly - tight under 10 reps, drifting beyond. Your last lift is remembered on the device, so week-to-week progression means editing one number. It pairs with the macro calculator for the kitchen half of the training equation.
How to use
- Enter the weight you lifted and the reps you completed with good form.
- Read your estimated 1RM - three formulas plus their average.
- Use the percentage working weights (80% for 5x5) to set your program.
Frequently asked questions
What is a one rep max?
The heaviest weight you can lift for a single clean repetition. It anchors strength programming: a 5x5 squat block at 80% of 1RM, a peaking block walking 90-95%. Testing it directly is exhausting and risky, which is why formulas estimate it from sets of 1-10 reps.
Which 1RM formula is most accurate?
For under 10 reps, Brzycki and Epley land within a couple of percent of each other; above that, Epley runs high because rep endurance inflates it. Averaging Epley, Brzycki and Lander - what this calculator does - hedges the extremes and matches how most programs publish their percentages.
How do I use percentages of my 1RM?
Strength blocks cluster at 80-90% (reps drop to 3-5), hypertrophy at 65-80% (reps 6-12), and technique or deload work sits around 60%. The 80% figure shown is the classic 5x5 working weight - heavy enough to force adaptation, light enough to accumulate volume.
Do these formulas work for women and for all lifts?
They were built mostly on male squat/bench/deadlift data and hold well there; for upper-body lifts and female lifters they tend to read slightly low at higher reps. Treat the output as a training anchor - a number to round your programming against - rather than a laboratory measurement.