One Rep Max (1RM) Calculator
Estimate a one-repetition maximum from the weight and repetitions of a completed set.
Estimate your 1RM from a working set
A technically consistent set of about two to ten reps usually gives a more useful estimate than a high-repetition set. Use the result to plan training loads; do not treat a formula estimate as a reason to attempt an unsafe maximal lift.
On this page
What this calculator estimates
Estimate a one-repetition maximum from the weight and repetitions of a completed set. The tool also shows 90%, 80% and 70% training-load comparisons.
Inputs and calculation method
Enter the total load in kilograms and completed repetitions. For more than one repetition the page uses the Epley equation. When repetitions equal one, it uses the entered weight directly. Displayed loads are rounded to the nearest 2.5 kg.
Formula and units
For repetitions above one, estimated 1RM = load × (1 + repetitions ÷ 30). For one repetition, 1RM = load. Each comparison is calculated from the rounded estimated 1RM and then rounded to the nearest 2.5 kg.
How to use it
- Use a completed set with consistent technique and range of motion.
- Enter total load in kg, including the bar when relevant.
- Enter the repetitions completed in that set.
- Read the rounded estimate and comparison loads; do not treat them as instructions to attempt a maximum.
Worked example
A set of 60 kg for 8 repetitions gives 60 × (1 + 8 ÷ 30) = 76 kg before rounding. The main result is 75 kg. The displayed 90%, 80% and 70% loads are 67.5 kg, 60 kg and 52.5 kg respectively.
How to read the result
The result estimates performance in the same exercise. It does not transfer directly between a machine and a free-weight version, or between different techniques. A comfortable set far from failure supplies less information about maximum performance.
Common mistakes
- Entering the weight of one dumbbell when the intended load is the combined total.
- Using partial repetitions to estimate a full-range maximum.
- Assuming an estimated maximum is safe to lift without preparation.
Method limitations
The Epley estimate is a mathematical extrapolation. High-repetition sets, fatigue, exercise choice and technique can widen the error; no injury or readiness assessment is performed.
Supporting guides for this calculator
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One Rep Max (1RM) Calculator FAQs
Why is my result a multiple of 2.5 kg?
The interface rounds the estimate and each percentage load to 2.5 kg increments.
What happens for a one-rep set?
The tool uses the entered load directly before rounding, rather than adding the Epley repetition allowance.
Does this calculate a training program?
No. The percentages are arithmetic comparisons, not a prescribed number of sets, repetitions or sessions.
Using the estimate
Use the same exercise and technique to compare estimated strength across sets. The calculated maximum remains an estimate rather than a recommendation to test it.