TrainersBookOne rep max calculator (1RM)
Estimate your one rep max from a normal set, without testing a true max. You also get a chart of training weights by percentage.
How it is calculated
The calculator averages two well-known formulas:
- Epley: weight × (1 + reps / 30)
- Brzycki: weight × 36 / (37 − reps)
They agree closely up to about 10 reps and drift apart above that. Use a hard set of 3–8 reps with good form for the most useful number.
How to use the percentage chart
Most strength programs are written in percentages of 1RM. The chart shows the weight for each percentage, rounded to the nearest 2.5 kg or 5 lb, and roughly how many reps most people can do at that load.
| Goal | Typical load |
|---|---|
| Max strength | 80–90% for 2–6 reps |
| Muscle building | 65–80% for 6–12 reps |
| Technique and speed | 60–70% for few, fast reps |
Reps at a given percentage differ between people and between lifts. Many people can do more reps at 70% on a leg press than on a bench press. Treat the rep column as a guide.
Estimate or test?
An estimate is safer and quicker than testing a true max, and it is good enough for planning training. If you do test, warm up well, use safeties or a spotter, and stop when the bar speed slows clearly.
Track it over time
Your estimated 1RM going up over months is one of the clearest signs that training works. A workout tracker keeps the history, and progressive overload explains how to keep it moving.
Common questions
What is a one rep max?
The heaviest weight you can lift once with good form. It is used to plan training loads as percentages.
How accurate is a 1RM calculator?
Within a few percent for most people when the set is 3–8 reps taken close to failure. Accuracy drops with more reps.
Which lifts can I use it for?
Any lift you can load, such as squat, bench press, deadlift or overhead press. It is less useful for bodyweight exercises.
How often should I recalculate?
Every four to eight weeks, or when your working sets clearly feel lighter.