1RM calculator
Your one-rep max (1RM) is the heaviest weight you can lift for a single rep. Enter a weight and how many reps you did with it, ideally 2–10, and this calculator estimates your 1RM and the loads to train with.
How the 1RM is estimated
Testing a true max takes a long warm-up and some nerve. An estimate from a hard set is quicker and close enough for planning. The calculator uses two well-known formulas and shows their average as your estimated 1RM.
Epley: 1RM = weight × (1 + reps ÷ 30)Brzycki: 1RM = weight × 36 ÷ (37 − reps) Example: 100 kg for 5 reps gives 116.7 kg (Epley) and 112.5 kg (Brzycki), so an estimate of about 114.6 kg.
Sources: Brzycki (1993), Strength testing: predicting a one-rep max from reps-to-fatigue; LeSuer et al. (1997), The accuracy of prediction equations for estimating 1-RM performance in the bench press, squat, and deadlift
Which is more accurate? Below 10 reps, Epley gives slightly higher numbers and Brzycki slightly lower; at exactly 10 reps they agree. Both get less reliable as the reps go up, which is why the calculator flags any set over 10. Studies comparing these equations found they predict best from lower-rep sets, and that accuracy varies between lifts such as the bench press, squat and deadlift.
Weren’t at failure? Pick how hard the set felt. RPE 8 means you had about 2 reps left, so 5 reps at RPE 8 is counted as 7 reps to failure. This is the reps-in-reserve scale most coaches use.
Using percentages in your training
Most strength programmes are written as a percentage of your 1RM. The table under your result rounds each load to the nearest 2.5 kg (or 5 lb), so you can load the bar straight from it. The “rough reps” column is about how many reps that load allows when you push close to failure.
Worked example: 5×5. A classic 5 sets of 5 sits around 80–85% of your 1RM. With an estimated 1RM of 115 kg, that’s roughly 92.5–97.5 kg. Start at the lower end: if all 25 reps feel solid, add 2.5 kg next session.
| Goal | Typical % of 1RM | Typical reps per set |
|---|---|---|
| Maximal strength | 85–95% | 1–5 |
| Strength and size | 75–85% | 5–8 |
| Muscle growth | 65–75% | 8–12 |
| Technique and warm-ups | 50–65% | 5–10, well short of failure |
Is it safe to test a true 1RM?
For a healthy, experienced lifter with good technique, yes, if you set it up properly. 1RM testing is also very repeatable: a systematic review found results are highly consistent from one test to the next. If you’re new to lifting, the estimate on this page is the better choice for now.
- Warm up with gradually heavier singles, for example 50%, 70%, 80% and 90% of your estimate.
- Use safety bars, or a spotter who knows what they’re doing, for squat and bench.
- Rest 3–5 minutes between heavy attempts, and stop when your form breaks down.
Track your 1RM over time
Your max goes up as you train, so this number goes out of date. Get Gains logs every set and spots new PBs automatically, so your estimated max for each lift stays current without the maths. It’s free to download on Android.
Planning more than your lifts? See all our free fitness calculators.