Enter the weight and reps from a set you completed: the calculator estimates your one rep max using the three reference formulas, shows the spread between them, and gives you the corresponding percentage chart.
Estimated 1RM (average of three formulas)
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Percentage chart
| % of 1RM | Load | Typical reps |
|---|
Read this before using the number. A 1RM estimate holds up to five or six reps, is workable to ten, and becomes guesswork beyond that. The typical rep counts in the chart are population averages: your own number can be double someone else's at identical relative intensity.
How the three formulas work
All three take the same two inputs — weight lifted and reps completed — and extrapolate what you could manage for a single rep. They disagree, and the disagreement is informative.
Epley is linear and tends to run high on higher rep sets. Brzycki is more conservative and holds up well in the one-to-ten range. Lombardi uses a power curve and sits between the two. The tool averages all three and shows you the spread, because the spread is the honest measure of how much the estimate should be trusted.
When three formulas built on the same data disagree by eight kilos, that gap is not noise to be smoothed away. It is the uncertainty, made visible.
What this number does not tell you
Two lifters with an identical true 1RM can produce very different rep counts at 70% of it. Richens and Cleather found reps to failure at 70% 1RM ranging from roughly seven to more than twenty in the same cohort. The relationship between percentage and reps is deeply individual.
It also varies by exercise. You will grind out far more reps at a given relative intensity on a leg press than on a bench press — larger muscle mass, more stable position, less technical failure. A single percentage chart cannot capture that.
What an estimated 1RM is genuinely good for
Two things, and they are worth having:
- Comparing yourself to yourself over time. If the same set of eight moves from 80 to 90 kg, the estimate climbs and confirms what you already suspected. It is a progress marker, not a prescription.
- Setting a starting point on a new exercise. Rather than guessing blind on your first session, an estimate gives you a defensible opening weight to adjust from.
What it is not good for is programming your entire training block in percentages. That approach assumes a stable, individual relationship between load and reps that most people simply do not have.
The method that skips the maximum entirely
There is a way to auto-regulate load without ever testing a true one-rep max, and without trusting a formula: reps in reserve. You judge how many reps you had left at the end of a set, and adjust the next session from there.
It costs nothing, it carries no injury risk, and it adapts to the day you are actually having rather than the day the spreadsheet assumed. It is also, not coincidentally, how RyzeFit sets your loads.
Related
- Should you test your 1RM? — the risk-reward case in full.
- Reps in reserve, explained — the alternative to percentages.
- Volume calculator — the load matters less than the number of sets.
- When to add weight — what to do with the number once you have it.
Frequently asked questions
How do I calculate my one rep max without testing it?
Take a set you completed with good form, enter the weight and the reps, and the calculator extrapolates using the Epley, Brzycki and Lombardi formulas. Accuracy is good up to five or six reps, acceptable to ten, and unreliable beyond that.
Which 1RM formula is most accurate?
None is reliably best across every lifter and lift. Brzycki tends to be conservative and performs well in the one-to-ten rep range; Epley runs higher on longer sets; Lombardi sits between them. Averaging all three, and looking at how far apart they are, is more honest than picking a favorite.
Why do the three formulas give different results?
Because each assumes a slightly different shape for the load-rep relationship, and that relationship varies between people. The spread between the three is a useful signal: a wide spread means the estimate deserves less confidence.
Should I actually test my one rep max?
Rarely, and only if you compete in a sport that requires it. For hypertrophy and general strength the risk-reward is poor: a true maximum attempt carries injury risk and produces a number you can estimate closely enough from a set of five.
How many reps can I do at 70% of my 1RM?
Anywhere from about seven to over twenty, depending on the individual and the exercise. Population averages put it near twelve, but the variation around that average is large enough that you should use your own experience rather than the chart.