🏋️One Rep Max Calculator
Estimate your 1RM from a working set — no risky max-out needed. Enter the weight you lifted and how many clean reps you did; the calculator runs five validated formulas and builds a training-percentage table instantly.
Estimated 1RM
Epley
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kg
Brzycki
—
kg
Lander
—
kg
Lombardi
—
kg
O'Conner
—
kg
Average
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kg
Training percentages
| % of 1RM | Weight | Use |
|---|
1RM estimates are a general reference only — not medical advice. Results are most accurate from sets of 2–6 reps and become less reliable above 10 reps. Always warm up progressively before heavy lifting, use proper technique, and use a spotter for any near-maximal or heavy sets. Lift within your current ability. If you have a heart condition, injury, or any health concern, consult a physician before training at high intensity.
Free One Rep Max Calculator Online
Want to know your max without risking a max-out? Our free One Rep Max Calculator estimates it from a normal working set. As a reliable one rep max calculator, you just enter the weight you lifted and how many clean reps you managed, and it estimates the most you could lift for a single rep — no failed lifts, no spotter, no risk of grinding out a true max alone.
It runs your set through several proven formulas — Epley, Brzycki, Lander, Lombardi, and O'Conner — and shows them side by side plus an average, so you get a balanced estimate rather than one formula's bias. It then builds a training-percentage table from 50% to 95%, with notes on what each band is good for, so you can pick working weights for strength, hypertrophy, or peaking. Switch between kg and lb and label the lift to track progress.
Simply enter your weight and reps to see your estimated max instantly. No sign-up, no downloads, no limits — just clear numbers whenever you need them. Read more on the FAQ or About pages.
About the One Rep Max Calculator
Key features
Five validated formulas + average
Epley, Brzycki, Lander, Lombardi, and O'Conner are all shown side by side so you can see where they agree and where they diverge. The average reduces any single formula's bias.
Training-percentage table
50–95% of the average 1RM with use-notes for warm-up, hypertrophy, strength, and peaking. Updates instantly as you change inputs so you never need to calculate percentages manually.
kg and lb support
Toggle between kilograms and pounds freely. Conversion is handled internally so the formula results and percentage table always match the selected unit.
Per-lift labelling
Label the result as bench press, squat, deadlift, overhead press, barbell row, or any custom lift to keep results organised when testing multiple movements.
High-rep accuracy warning
The tool warns you when you enter more than 10 reps, where formula accuracy degrades. Reps are clamped to a maximum of 12 to prevent wildly unreliable estimates.
Instant, private, no sign-up
Results update as you type. Your inputs are never stored or sent anywhere. Open the page and use it — no account or setup needed.
The formulas
All five formulas take a submaximal weight (w) and rep count (r) and return an estimated 1RM. They were each derived from experimental data and are cited across sports science literature. When reps = 1 the calculator returns the entered weight directly, since that is by definition your observed maximum for that set.
Epley (1985)
w × (1 + r / 30) — one of the oldest and most cited. Tends to give slightly higher estimates at higher rep counts.
Brzycki (1993)
w ÷ (1.0278 − 0.0278 × r) — popular in powerlifting. Agrees closely with Epley at 2–6 reps and diverges above 10.
Lander (1985)
(100 × w) ÷ (101.3 − 2.67123 × r) — derived from a different dataset, generally falls between Epley and Brzycki.
Lombardi (1989)
w × r^0.10 — a power-based model; tends to give higher estimates than the linear formulas, especially at higher reps.
O'Conner et al. (1989)
w × (1 + 0.025 × r) — a conservative formula that tends to give lower estimates; useful as a lower bound.
Average of five
The mean of all five results. Using an average reduces the individual error of any one formula and is the basis for the training-percentage table.
Accuracy and limitations
Estimates are most reliable for sets of 2–6 reps performed close to failure with proper form. Accuracy decreases above 10 reps because the rep–max relationship becomes less predictable and more individual. The tool warns you when reps exceed 10 and clamps input to 12.
Individual factors — technique, muscle fibre composition, fatigue, and the specific exercise — all affect how close a formula estimate is to your true maximum on a given day. Use the estimate for programming reference, not as a number to chase recklessly.
Frequently Asked Questions
What is a one rep max?
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."
How does the calculator estimate my 1RM?
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.
Why not just test my actual 1RM?
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.
Which formula is most accurate?
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.
Is this calculator free to use?
Completely free — no sign-up, no downloads, and no limits. Use it as many times as you like on any device.
How many reps should I use for the best accuracy?
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.
What is the training-percentage table for?
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.
Can I use kg or lb?
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.
Is my data stored or shared?
No. All calculations happen directly in your browser. Your inputs are never sent to a server or stored anywhere.
Is it safe to lift to these estimated weights?
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.