One-Rep Max (1RM) Calculator
Estimate your one-rep max — the most weight you could lift for a single rep — from a weight you lifted for multiple reps, using the Epley, Brzycki, Lombardi, and other proven formulas. A safe way to gauge maximal strength without testing a true 1RM.
How to Use
- Enter the weight you lifted (use any unit — the result comes back in the same unit).
- Enter the number of clean reps you completed with that weight, ideally between 2 and 10.
- Read your estimated one-rep max, shown for each formula (Epley, Brzycki, Lombardi, and more).
- Use the formulas that cluster together as your best estimate; outliers usually appear at very high rep counts.
- Try a preset like "Bench 225×5" or "Squat 315×3" to see how reps and load drive the estimate.
Show Work
Formulas
About the One-Rep Max (1RM) Calculator
One-Rep Max (1RM) Calculator is a quick, free tool for health and fitness tracking. It works in your browser and keeps everything on your device. Estimate your one-rep max — the most weight you could lift for a single rep — from a weight you lifted for multiple reps, using the Epley, Brzycki, Lombardi, and other proven formulas. A safe way to gauge maximal strength without testing a true 1RM.
How it works
Enter your figures and the result appears instantly, updating the moment you change anything. There is no submit button and nothing to wait for, so it is easy to try a few what-if numbers and compare the results. Just check each box holds the kind of value it expects.
Want the deeper story? The Knowledge Base explains the ideas behind the tools in more detail.
Frequently Asked Questions
What is a one-rep max?
Your one-rep max (1RM) is the heaviest weight you can lift for a single repetition with good form on a given exercise. It is the standard benchmark of maximal strength and is used to set training percentages — for example, working sets at 70–85% of 1RM. This calculator estimates it from a submaximal set so you do not have to attempt a risky true max.
How accurate are 1RM estimates?
They are most accurate in the 2–10 rep range and tend to agree within a few percent there. Beyond about 10 reps, the estimates diverge and overstate true max because endurance and fatigue increasingly affect performance. For the best estimate, use a set you took close to failure with a moderate rep count.
Why do the formulas give different numbers?
Each formula (Epley, Brzycki, Lombardi, and others) was fit to different data and makes slightly different assumptions about how strength drops off as reps rise. Epley and Brzycki are the most popular and usually land within a few pounds of each other. Looking at several at once gives you a sensible range rather than a single false-precision figure.
Should I actually test my true 1RM?
Estimating is safer and sufficient for most lifters. A true max attempt carries higher injury risk and requires a thorough warm-up, ideally a spotter, and good technique under fatigue. Competitive powerlifters test maxes periodically, but most people can program effectively using estimated 1RMs from regular working sets.
How do I use my 1RM for programming?
Most strength programs prescribe loads as a percentage of 1RM — for example 5×5 around 80%, or hypertrophy work at 65–75%. Recalculate periodically as you get stronger so your percentages keep pace. Many lifters update their estimated 1RM whenever they hit a new rep PR on a key lift.
How do I use the One-Rep Max (1RM) Calculator?
Just type your numbers. The answer shows up right away — there is no button to press. Change anything and it updates by itself.
Does it cost anything or need an account?
No. The tool is completely free, there is no account to create, and it keeps working offline after the page first loads.
Is anything I type uploaded?
No. The tool works entirely on your device, so the values you enter never leave your browser.
Common Use Cases
Setting training percentages
Convert a recent working set into a 1RM to program loads as a percentage.
Tracking strength progress
Estimate 1RM over time to see strength gains without maxing out each week.
Comparing lifts safely
Gauge maximal strength on bench, squat, or deadlift without a risky single.
Planning a peak or test day
Predict a realistic top attempt before a true 1RM test or competition.
Auto-regulating sessions
Re-estimate after a strong set to adjust the day’s working weights on the fly.
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