What’s your one-rep max? This free 1 rep max calculator estimates your 1RM from a weight and reps using the Epley and Brzycki formulas, plus a percentage table for picking training weights – no max attempt needed.
Enter a weight and the reps you completed with good form (ideally under 10 for accuracy). Your one-rep max is estimated – don’t attempt a true max without proper warm-up and a spotter.
An estimate from a rep test – accuracy is best at lower reps and drops as reps rise. Use percentages as a starting point for programming, and always train with good form and safety.
How the 1 Rep Max Calculator Works
The 1 Rep Max Calculator estimates your one-rep max from a weight and rep count you’ve already lifted, using two well-known rep-max formulas, so you don’t have to attempt an actual maximal lift to plan your training.
Formula: Epley 1RM = Weight × (1 + Reps ÷ 30). Brzycki 1RM = Weight × 36 ÷ (37 − Reps). The calculator’s estimated 1RM is the average of the two: (Epley + Brzycki) ÷ 2. When Reps = 1, the estimated 1RM is simply the weight entered. A percentage table then multiplies that 1RM by 100%, 95%, 90%, 85%, 80%, 75% and 70% to suggest training weights for roughly 1, 2, 4, 6, 8, 10 and 12 reps.
- Weight lifted — the load you lifted, in kg or lb (toggle the unit button)
- Reps performed — how many reps you completed with that weight using good form, ideally fewer than about 10 for best accuracy
Example Scenarios
| Weight | Reps | Estimated 1RM |
|---|---|---|
| 100 kg | 5 | 114.6 kg |
| 60 kg | 10 | 80.0 kg |
| 80 kg | 1 | 80.0 kg |
| 140 lb | 8 | 175.6 lb |
| 225 lb | 3 | 242.9 lb |
1 Rep Max Calculator FAQ
How accurate is an estimated 1RM compared to actually testing it?
Rep-max formulas like Epley and Brzycki are estimates built from submaximal sets; they tend to be closest when you test with fewer reps (roughly under 6-8) and can drift further from your true max as rep count rises.Why do Epley and Brzycki give different numbers for the same lift?
They’re two separate formulas built from different assumptions about how strength drops off as reps increase, so they rarely land on the exact same number – averaging them is one way to split the difference.Is it safe to attempt a true 1-rep max in the gym?
Max-effort singles carry real injury risk, especially without a spotter, proper warm-up or supervision – beginners or anyone with a medical condition are better off estimating from a submaximal set like this calculator does, and should check with a doctor or trainer before attempting a true max.What rep range gives the most reliable 1RM estimate?
Lower rep counts (roughly 1 to 6) tend to produce more reliable estimates than higher ones, since fatigue and technique breakdown have more influence on performance the longer a set goes.How do I use the percentage table to plan my training?
Each row estimates the weight for a target rep range (for example, around 80% of your 1RM for about 8 reps), which you can use as a starting point for programming sets – actual performance still varies by exercise and day.Does this work for any exercise, or just squat, bench and deadlift?
The math is generic to any barbell or resistance exercise, but the underlying formulas were developed mainly from major compound lifts, so estimates for smaller isolation movements may be less precise.Related Calculators
To put your estimated max to work, the Workout Volume Calculator can total up the sets and reps in a training session, while the Push Up Calorie Calculator and Wall Sit Calorie Calculator cover the bodyweight side of a strength routine.