One-rep max calculation examples
| Weight | Reps | Estimated 1RM |
|---|---|---|
| 80 kg | 8 | 101.3 kg |
| 85 kg | 5 | 99.2 kg |
| 92.5 kg | 8 | 117.2 kg |
| 100 kg | 5 | 116.7 kg |
| 100 lb | 5 | 116.7 lb |
Switching kg/lb changes the unit label; it does not convert the number entered. Use the weight in your chosen unit. With zero weight the result is zero. With one rep, the unchanged Epley equation returns 1.033 times the weight; a tested 100 kg single is still a tested 100 kg single.
What formula does this 1RM calculator use?
According to Boyd Epley (1985), estimated 1RM = weight × (1 + reps / 30). This page uses that equation, matching Setlane. Wikipedia’s one-repetition maximum article documents the same formula. Public values in the app are rounded to one decimal place; the calculator does the same. There is no repetition cap.
e1RM = weight × (1 + reps / 30)
A worked 92.5 kg × 8 example, plus the bibliographic sources, is in the e1RM guide.
How accurate is an estimated one-rep max?
Accuracy depends on the exercise, rep range and how close the set was to your limit. The equation does not know effort, rest time or range of motion. Reynolds, Gordon and Robergs (2006) found 5RM data predicted bench and leg-press 1RM more accurately than 10RM or 20RM data in their study. That does not give every Epley estimate a fixed error margin.
The high-rep reminder on this page appears above 10 reps as a practical caution, not a boundary between accurate and inaccurate results. The calculation is still the same. Read the e1RM guide and worked trend for more context.
The calculator does not write to your account. To follow the sets over time, log them in Setlane and compare progress across completed workouts.
Frequently asked questions
What formula does this one-rep max calculator use?
Epley: estimated 1RM = weight × (1 + reps / 30). The result is rounded to one decimal place, matching Setlane. Enter a non-negative weight and a positive whole number of reps. The same equation is applied at one rep; there is no repetition cap.
Does the kg/lb switch convert my weight?
No. It changes the unit label. Enter the weight in the unit you choose; the estimated result uses that same unit.
Does this calculator save my workout or require an account?
No. It calculates an estimate in your browser. It does not save a workout to Setlane and does not require a login.