Free tool
One-Rep Max (1RM) Calculator
Estimate your one-rep max from any hard set of 1–12 reps — no risky max-out needed. You get your estimated 1RM, a comparison of three common formulas, the load for every training percentage from 100% down to 50%, and your estimated rep maxes.
Estimated 1RM
265 lb
Epley formula, from 225 lb × 5
Formula comparison · All values are estimates.
- Epley265 lb
- Brzycki255 lb
- Lombardi265 lb
Percentage of 1RM
| % of 1RM | Load | Typical reps |
|---|---|---|
| 100% | 265 lb | 1 |
| 95% | 250 lb | 2 |
| 90% | 235 lb | 3–4 |
| 85% | 225 lb | 5–6 |
| 80% | 210 lb | 7–8 |
| 75% | 195 lb | 9–10 |
| 70% | 185 lb | 11–12 |
| 65% | 170 lb | 13–15 |
| 60% | 160 lb | 15–20 |
| 55% | 145 lb | 20+ |
| 50% | 130 lb | 20+ |
Estimated rep maxes
The most you could expect to lift for each number of reps.
| 1 rep | 265 lb |
|---|---|
| 2 reps | 245 lb |
| 3 reps | 240 lb |
| 4 reps | 230 lb |
| 5 reps | 225 lb |
| 6 reps | 220 lb |
| 7 reps | 215 lb |
| 8 reps | 205 lb |
| 9 reps | 200 lb |
| 10 reps | 195 lb |
| 11 reps | 190 lb |
| 12 reps | 190 lb |
How to use the 1RM calculator
- Pick a recent set you took close to failure — ideally 3–8 reps with good form.
- Enter the weight on the bar (or one dumbbell) and the number of clean reps you completed.
- Choose kg or lb. The calculator remembers your choice for next time.
- Read your estimated 1RM, then use the percentage table to pick working weights for your next sessions.
Worked example
Say you bench 225 lb for 5 hard reps. With the Epley formula your estimated 1RM is 225 × (1 + 5 ÷ 30) ≈ 262.5 lb. Brzycki gives about 253.1 lb and Lombardi about 264.3 lb — close enough that any of them works, as long as you stick to one.
If your program calls for sets at 80% of 1RM, that's about 210 lb, or 210 lb once rounded to loadable plates. And the rep-max chart suggests you could manage around 205 lb for 8 reps.
The 1RM formulas explained
Each formula turns a weight (w) lifted for a number of reps (r) into an estimated single-rep max. They were fitted to different groups of lifters, so they agree closely at low reps and drift apart as reps go up.
Epley
1RM = w × (1 + r ÷ 30)
The most widely used formula and the default here. It assumes each extra rep adds about 3.3% to your max.
Brzycki
1RM = w × 36 ÷ (37 − r)
Slightly more conservative than Epley between 2 and 9 reps; the two give the same answer at 10 reps, and Brzycki climbs faster above that.
Lombardi
1RM = w × r^0.10
A power curve that rises more slowly at higher reps, so it gives the lowest estimates of the three from 10 reps upwards.
No formula is "correct" for everyone. Pick one and use it consistently so your estimated 1RM trend stays comparable over time.
Read the full guide: how to calculate your one rep max →
Assumptions and limits
These numbers are estimates based on population averages. Your true max can be higher or lower depending on training experience, the exercise, muscle fibre make-up and how close to failure your set really was.
The results are a reference point, not a training prescription. Adjust loads to how the weight actually moves on the day.
Always warm up before heavy sets, progress gradually, and use a spotter or safety pins for heavy barbell work. If you have an injury or a medical condition, check with a qualified professional first.
Frequently asked questions
What is a one-rep max (1RM)?
Your one-rep max is the heaviest weight you can lift for a single complete repetition with good form. Many strength programs set training loads as a percentage of it.
How accurate is a 1RM calculator?
For hard sets of about 2–10 reps, formula estimates usually land close to a tested max, but individual results vary. Accuracy drops as reps increase, which is why the calculator warns above 10 reps.
Which 1RM formula is best?
There is no single best formula. Epley and Brzycki are the most common and give very similar results for low-rep sets. Consistency matters more than the choice: use the same formula every time you compare your progress.
How many reps should I use to estimate my 1RM?
A set of 3–8 reps taken close to failure gives the most reliable estimate. Very light sets with many reps left in reserve will underestimate your max.
Should I test my true 1RM instead?
Testing a true max is a skill and carries more risk, especially without a proper warm-up, spotter or experience with maximal attempts. For most lifters an estimate from a hard set is enough to plan training.
How do I use percentages of my 1RM?
Programs often prescribe roughly 80–90% of 1RM for low-rep strength work and 65–80% for moderate-rep muscle-building work. Use the percentage table to turn those numbers into loads, then adjust to how the sets feel.
Does the calculator work for dumbbell and machine exercises?
Yes. Enter the load you actually moved — the weight of one dumbbell, or the stack weight on a machine. Estimates are most reliable on compound lifts and less precise on small isolation exercises.
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Keep your numbers in one place
GymMonster is a free workout tracker for iOS and Android. Log your sets, follow your routines and watch your personal records climb — so your next 1RM estimate is one glance away.
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