Free calculator
One-rep max calculator
By Caleb King, founder of CoachhUpdated Formula: Epley, or a reps-in-reserve chart
Your one-rep max is the most you can lift once with good form. You can estimate it from one hard set instead of testing it: the Coachh app uses Epley's formula, weight × (1 + reps ÷ 30), for 1 to 12 reps, or a reps-in-reserve chart when you know how many reps you had left. 185 lb for 5 reps estimates about 216 lb.
One-rep max calculator
Your estimated max from one hard set, and what to load for other rep counts. Nothing you enter leaves this page.
About 215.8 lb estimated one-rep max
Epley: 185 × (1 + 5 ÷ 30).
| Reps | Last rep is a grind | 2 reps left |
|---|---|---|
| 1 | 215 lb | 200 lb |
| 2 | 205 lb | 190 lb |
| 3 | 200 lb | 185 lb |
| 4 | 190 lb | 180 lb |
| 5 | 185 lb | 175 lb |
| 6 | 180 lb | 170 lb |
| 8 | 170 lb | 160 lb |
| 10 | 160 lb | 145 lb |
| 12 | 145 lb | 135 lb |
An estimate, not a test. Don’t attempt a true one-rep max without a spotter and safety bars, and skip max attempts while you’re injured or sore.
How does the one-rep max calculator work?
It uses the same two methods as the Coachh app:
- Epley’s formula when you don’t say how hard the set was: estimated max = weight × (1 + reps ÷ 30). A single is its own max, and the app doesn’t estimate from sets over 12 reps.
- A reps-in-reserve chart when you do. Reps done plus reps left is reps to failure, and the chart gives the share of your max you can lift for that many: 5 reps with 2 left is 7 to failure, 81.1%. Estimated max = weight ÷ that share.
Reps in reserve comes from the RPE scale strength coaches use: a 2016 study tested lifters rating each set by how many reps they had left, and a companion article describes using it to set loads set by set.
What does a worked example look like?
You bench 185 lb for 5 reps and the last one was hard:
- Epley: 185 × (1 + 5 ÷ 30) = 185 × 1.167 = 215.8 lb.
- If you’d had 2 reps left: 7 to failure, 81.1%, so 185 ÷ 0.811 = 228.1 lb.
The two agree when the set goes to failure (Epley 215.8, the chart 214.4 for 5 reps with none left) and differ when you stop short, which is why the app asks how a set felt.
What percentage of your max can you lift for each rep count?
The chart Coachh uses beside Epley’s formula, for sets taken to failure, and the weight each gives from a 225 lb max:
| Reps | Coachh's chart | Epley | From a 225 lb max |
|---|---|---|---|
| 1 | 100.0% | 100.0% | 225 lb |
| 2 | 95.5% | 93.8% | 215 lb |
| 3 | 92.2% | 90.9% | 205 lb |
| 4 | 89.2% | 88.2% | 200 lb |
| 5 | 86.3% | 85.7% | 195 lb |
| 6 | 83.7% | 83.3% | 190 lb |
| 7 | 81.1% | 81.1% | 180 lb |
| 8 | 78.6% | 78.9% | 175 lb |
| 9 | 76.2% | 76.9% | 170 lb |
| 10 | 73.9% | 75.0% | 165 lb |
| 11 | 70.7% | 73.2% | 160 lb |
| 12 | 68.0% | 71.4% | 155 lb |
How accurate is an estimated max?
Good enough to train with, not good enough to bet a meet on. In a 2006 study of 70 adults aged 18 to 69, the 5-rep max predicted the real 1RM best, with a typical error of about 3 kg on the bench press and about 16 kg on the leg press. The authors suggest no more than 10 reps for formulas like Epley’s.
- Use a heavy set of about 5 reps, done with good form: in that study, the 5-rep max predicted best.
- Estimates vary by lift: the same study’s leg press error was about five times its bench press error.
- Don’t chase a true max while injured, sore or without a spotter or safety bars.
Does Coachh track this for you?
Yes. Coachh does this for you every day: say “185 for 6” in the chat or log the set on your Apple Watch, and it works out the estimated max with this same math, calls out a new best, and charts the estimated max of your program’s main lifts once you’ve logged each one twice. Next session’s main-lift weight comes from that estimate and the effort your plan asks for, and never jumps more than 10% over your heaviest set last time. The honest limits: Apple Watch set logging is new in version 1.0, and an estimate is only as good as the sets you log. Read how Coachh works for how programs are written and adjusted.
Common questions
How accurate is a one-rep max calculator?
Close enough to plan training with, and better from fewer reps. In a 2006 study of 70 adults, a 5-rep max predicted the bench press 1RM with a typical error of about 3 kg, but the leg press with about 16 kg, and accuracy fell as the reps went up.
Should I test my real one-rep max?
Not for everyday training: an estimate from a heavy set is enough to pick your weights. If you do test, warm up well, use a spotter or safety bars, and never test through pain or an injury.
Why does the calculator stop at 12 reps?
Because the formulas drift further from a real max as the reps rise. The 2006 study suggests using no more than 10 reps for linear formulas like Epley's; the Coachh app stops counting a set toward your estimated max above 12.
What does reps in reserve mean?
How many more reps you could have done when you stopped the set: 0 means the last rep was all you had, 2 means you had two more. A 2016 study found the scale a practical way to set daily training loads, and it lets a set you stopped short of failure still estimate your max.
Sources
- Prediction of one repetition maximum strength from multiple repetition maximum testing and anthropometry. Journal of Strength and Conditioning Research (Reynolds JM, Gordon TJ, Robergs RA), 2006.
- Novel Resistance Training-Specific Rating of Perceived Exertion Scale Measuring Repetitions in Reserve. Journal of Strength and Conditioning Research (Zourdos MC et al.), 2016.
- Application of the Repetitions in Reserve-Based Rating of Perceived Exertion Scale for Resistance Training. Strength and Conditioning Journal (Helms ER et al.), 2016.