Free Tools
One-Rep Max Calculator
Enter a weight and the reps you hit, and we'll estimate your one-rep max across three proven formulas — then hand you the exact training loads for every percentage of that max.
No sign-up, no maths. Skip the risky true-max test and programme your sessions off a solid estimate instead.
Enter the weight and how many reps you hit to estimate your max.
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What is a one-rep max?
Your one-rep max, or 1RM, is the heaviest weight you can move for a single clean rep on a given lift. It's the reference point strength programmes are built on: once you know it, you can set every working weight as a percentage of it rather than guessing. Testing a true max is taxing and carries risk, so most lifters estimate it from a hard set of a few reps.
How the estimate works
We run your set through the Epley, Brzycki and Lombardi equations and average the result. Each formula was fitted to slightly different data and tends to over- or under-shoot at the edges, so the mean is steadier than any single one. The catch is universal: accuracy fades as reps rise. At five reps or fewer the number is tight; beyond ten to twelve it drifts, so we cap the input there.
Training off your percentages
The real payoff is the load table. Heavy strength work generally sits at 85% or more of your max for low reps; hypertrophy work lives around 70–80% for moderate reps. Plugging your estimated max into those percentages gives you concrete weights to load on the bar, session after session, instead of chasing a feeling.
Common questions
How do you calculate a one-rep max?+
A one-rep max (1RM) is the most weight you can lift for a single rep. Rather than testing a true max, which is fatiguing and risky, you can estimate it from a submaximal set. Our calculator averages three established formulas — Epley, Brzycki and Lombardi — because each drifts slightly differently and the mean is more reliable than any one alone.
How accurate is an estimated 1RM?+
Very accurate at low reps and less so as reps climb. Estimates are most reliable at about 5 reps or fewer; past 10 to 12 reps, form breakdown and endurance start to distort the number, which is why we cap the input at 12 reps. Treat the figure as a close training guide, not a certified max.
What are the percentages for?+
Once you know your 1RM, you can programme every session off it. Heavy strength work typically sits at 85 percent or more of your max for low reps, while muscle-building work lives around 70 to 80 percent. The load table turns your estimated max into the exact working weights for each percentage.
Which supplements actually help me lift more?+
For raw strength and power, creatine monohydrate is the most evidence-backed supplement there is, at 3 to 5 grams a day. A caffeinated pre-workout can also lift acute performance and perceived effort. Everything else is a distant second to consistent training, sleep and enough protein.
Is this medical or coaching advice?+
No. It is a general, evidence-based training tool for healthy adults, not personalised coaching or medical advice. Always warm up, use a spotter or safety pins when working near your max, and stop if a lift feels unsafe.
Want to move the number?
Training drives strength — but creatine and a solid pre-workout are the two supplements with real evidence behind them. Every product we track is scored 0–100 on how closely its doses match that evidence.
Informational only — not medical or coaching advice. Warm up, use safety pins or a spotter near your max, and stop if a lift feels unsafe. Buy links are affiliate links; we may earn a commission at no extra cost to you.