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One Rep Max Calculator
with Multi-Formula Strength Estimates

Estimate your one rep max from weight and reps using several common strength formulas, then view rep max projections and training percentages.

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One Rep Max Calculator
EX
Used only for context in the output.
kg
Enter the load you actually lifted for the completed reps.
reps
Best used for sets of about 1 to 10 reps. Estimates become weaker at higher reps.
fx
Controls which estimate is highlighted as the main result.
🎯
Used to highlight a suggested training percentage range.
Method note
This calculator compares multiple one rep max formulas. For heavier sets with fewer reps, the estimates are generally more stable than for high-rep sets.
Estimated One Rep Max
—
selected formula focus
Average Estimate
—
average of all formulas
Lowest Estimate
—
most conservative formula in this result
Highest Estimate
—
most aggressive formula in this result
Suggested Working Range
—
highlighted from selected training goal
Epley
—
Common estimate for low to moderate reps.
Brzycki
—
Widely used in strength settings.
Lombardi
—
Uses an exponential rep relationship.
Mayhew
—
Often referenced for pressing estimates.
O'Conner
—
Simpler rep-adjusted estimate.
Wathan
—
Another widely cited strength formula.
Input summary
Exercise—
Weight lifted—
Reps completed—
Formula focus—
Training summary
Training goal—
Primary estimate—
Average estimate—
Suggested working range—
Rep Max and Training Percentage Table
Target Percentage Estimated Weight Common Use
One Rep Max Breakdown
Unit system—
Exercise—
Weight lifted—
Reps completed—
Epley—
Brzycki—
Lombardi—
Mayhew—
O'Conner—
Wathan—
Average estimate—
Lowest estimate—
Highest estimate—
Suggested working range—
One rep max formulas are estimation tools and are not exact guarantees. Results are generally more useful when based on technically solid sets in a lower rep range.
✦ Cal, AI Explanation
Cal is reviewing your one rep max result...
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Your one rep max result is ready. Ask me how the formulas differ, which number to trust most, or how to use the training percentages.

💡 1RM Notes

One rep max formulas estimate maximal strength from a submaximal set.
Lower-rep sets usually produce more stable 1RM estimates than very high-rep sets.
Different formulas can return slightly different values from the same set.
Using a formula average can reduce the effect of one unusually high or low method.
Training percentages are general planning tools, not exact prescriptions.

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Related Guides

One Rep Max Formulas Explained→ How to Use Training Percentages→ Estimating Strength Without Max Testing→

How one rep max is estimated here

This calculator estimates your one rep max from a completed set of weight and reps. Instead of relying on only one equation, it compares several common formulas including Epley, Brzycki, Lombardi, Mayhew, O'Conner, and Wathan.

Because these formulas use slightly different assumptions about how rep performance scales to maximal strength, their outputs are usually close but not identical.

Why multiple formulas are shown

One Rep Max = formula estimate from lifted weight and reps
Average Estimate = mean of all formula outputs
Working Weights = one rep max × training percentage
The average estimate can be a useful midpoint when no single formula is clearly preferred.

How training percentages are used

Training percentages convert the estimated one rep max into lighter planning weights. Lower percentages are commonly used for speed work, technique work, and higher-rep training. Higher percentages are more often used for heavier strength work.

This calculator highlights a suggested range based on the selected training goal, but the percentages themselves are still general planning tools.

Range Typical Use
60% to 70%Higher reps, technique, lighter volume
70% to 80%General strength and hypertrophy work
80% to 90%Heavier strength work
90%+Very heavy singles, doubles, or testing context

When the estimate is most useful

One rep max formulas are usually most useful when the input set is technically clean and not extremely high in reps. A lower-rep set often gives a more stable estimate than a long set close to failure.

The formulas shown here help you compare a range rather than assuming one exact number is always correct.

Frequently Asked Questions

Which one rep max formula is best?+
There is no single universal best formula. Different formulas can suit different rep ranges and lifting contexts, which is why this calculator shows several estimates and an average.
Why do the formulas give different results?+
Because each formula models the relationship between repetitions and maximal strength differently. The differences are usually moderate rather than extreme, especially in a lower rep range.
Should I test a real one rep max instead?+
A true max test measures actual maximal performance, while this calculator provides an estimate. The estimate is useful when you do not want to test a true maximum directly.
Are high-rep sets good for estimating one rep max?+
They can still produce an estimate, but the result usually becomes less reliable as reps get higher. Lower-rep sets often give a cleaner starting point for 1RM estimation.
What should I do with the training percentages?+
They can be used as reference weights for programming. Heavier percentages are generally used for heavier strength work, while lower percentages are more often used for lighter volume or technique practice.