One Rep Max Calculator — FAQ

Your one rep max (1RM) is the maximum weight you can lift for a single clean repetition of a given exercise. It is the standard benchmark of strength in weightlifting and powerlifting, and the basis for percentage-based training — programs that prescribe working weights like "lift 80% of your 1RM for 5 sets of 3."

You enter the weight you lifted and the number of clean reps you completed with that weight. The calculator applies five validated formulas — Epley, Brzycki, Lander, Lombardi, and O'Conner — to estimate the single-rep max from that submaximal set, and shows you each result side by side plus an average.

Testing a true 1RM is highly fatiguing, requires a spotter, and puts form under maximal stress — increasing injury risk, especially for less experienced lifters. Estimating from a 3–6 rep set is safer, avoids failed lifts, and gives a result that closely matches a true max under most conditions. It also lets you test progress without needing a dedicated max-out day.

At low rep counts (2–6 reps) all five formulas agree closely — often within a few percent of each other. Epley and Brzycki are the most widely cited in research. Averaging the five reduces any single formula's individual bias, which is why the calculator highlights the average as the primary reference. No single formula is universally best across all lifters, exercises, or rep ranges.

Completely free — no sign-up, no downloads, and no limits. Use it as many times as you like on any device.

Best results come from sets of 2–6 reps with a weight that genuinely challenges you — close to failure without actually reaching it. Accuracy is reasonable up to about 10 reps. Above 10 the estimate becomes increasingly unreliable because the submaximal rep–max relationship breaks down, so the calculator shows a warning if you enter more than 10 reps.

Most strength programs prescribe working weights as a percentage of your 1RM. The table shows 50–95% of your estimated average 1RM with notes on what each intensity zone is typically used for: warm-up at 50%, hypertrophy at 70–75%, strength at 80–85%, and peaking or near-maximal work at 90–95%. Use it to quickly look up the right weight for your training goal without needing to do the maths yourself.

Yes. Use the kg / lb toggle to switch units freely. You can also label the specific lift — bench press, squat, deadlift, overhead press, barbell row — to keep results organised when tracking progress across multiple movements.

No. All calculations happen directly in your browser. Your inputs are never sent to a server or stored anywhere.

Treat the estimate as a planning reference, not a target to chase without preparation. Always warm up properly, use good technique, and use a spotter for any near-maximal sets. If you have a heart condition, injury, or any health concern, get clearance from a physician before training at high intensity. This tool provides general information — not medical advice.