Free tool · No account
Estimate your 1RM from any set.
Enter a weight and the reps you hit. You get your estimated one-rep max across three standard formulas, and the training percentages that come with it. Nothing to install, nothing to sign.
Estimated 1RM
115.6kg
Average of the three formulas
By formula
- EpleyBalanced, the common default116.7 kg
- BrzyckiMore conservative on low reps112.5 kg
- LombardiRuns higher past 6 reps117.5 kg
Training percentages
Your working loads, straight from this estimated max.
| % | Load |
|---|---|
| 95% | 109.8 kg |
| 90% | 104 kg |
| 85% | 98.3 kg |
| 80% | 92.5 kg |
| 75% | 86.7 kg |
| 70% | 80.9 kg |
| 65% | 75.1 kg |
| 60% | 69.4 kg |
| 55% | 63.6 kg |
| 50% | 57.8 kg |
The basics
What a one-rep max actually is
Your one-rep max is the heaviest load you can lift once with clean form. It is the reference every training percentage is built on. Testing a true 1RM means grinding an all-out single, which needs a spotter and taxes your joints. An estimate skips that: you lift a submaximal set, and the math projects the single you would hit. For most lifters, most of the time, the estimate is enough to program from.
The math
Three formulas, three angles
Each formula reads the load-and-reps relationship a little differently. None is the truth; each is a solid projection. That is why this tool shows all three and leads with their average. On a set of 3 to 8 reps they land within a few percent of each other.
Epley: 1RM = weight × (1 + reps / 30)Brzycki: 1RM = weight × 36 / (37 - reps)Lombardi: 1RM = weight × reps^0.10
In practice
Estimate or test your max?
Estimate when you are programming, tracking progress, or training without a spotter. A hard set of 3 to 8 reps gives you a reliable number without the risk of a true single. Test a real 1RM only when it counts: a meet, a peak week, a supervised max-out. And keep the reps honest. Past about 12, fatigue muddies the projection and the estimate drifts.
1RM calculator: common questions
Within about 5% of a true max for sets of 3 to 8 reps, for most trained lifters. It drifts higher past 10 reps. Treat it as a close projection, not a certified number.
The one your program or coach already uses, so your numbers stay consistent. With no preference, go with the average, which is what this tool shows first.
Both. Pick your unit and every result, percentage table included, follows it. The formulas ignore the unit; only the ratio of load to reps matters.
They turn your max into working loads. 90% covers heavy singles and doubles, 70 to 80% is strength work, lower percentages build volume. Read them straight off the table.
No. The calculator runs entirely in your browser and sends nothing anywhere. The waitlist below is the only place you would leave an email, and only if you want the app.
The app
This is one set. The app does it for every set.
Hephast is an offline workout log that tracks your e1RM automatically, every set you confirm, and flags a new record the moment you beat it. Free, no account. Join the waitlist for launch.