One Rep Max Calculator
Estimate your one-repetition maximum (1RM) from a submaximal set and compare two common lifting formulas.
Estimate your 1RM
Use a recent set completed with controlled form.
Use estimates to guide training, not as a guarantee of a maximum lift.
Training loads by percentage
Use as a reference when planning submaximal sets.
| Percent of estimated 1RM | Estimated load | General use |
|---|---|---|
| 60% | — | Moderate load |
Percentages are planning aids; the right load also depends on repetitions, technique, fatigue and training experience.
How to use a one rep max calculator
🏋️ Choose a recent set
Enter the weight and number of repetitions you completed. The estimate is generally more useful when the set was challenging but performed with consistent technique.
⚖️ Select pounds or kilograms
Use the unit displayed on your plates or training log. Keep the unit consistent when comparing results over time.
📊 Compare the estimates
Epley and Brzycki use different equations, so their predictions can differ. A difference is normal and shows that 1RM calculators are estimates, not direct measurements.
🧭 Plan, don’t prove
Use your estimated max to set sensible starting loads. Do not feel required to attempt a true maximum to validate the number, especially without coaching or appropriate safety equipment.
What is a one-repetition maximum?
A one-repetition maximum, commonly written as 1RM, is the greatest load a person can lift once through a complete repetition with appropriate technique. Coaches and lifters use it as a reference for programming strength work. A direct 1RM test can be demanding, so a calculator estimates it from a lighter load and the number of repetitions completed.
Epley formula
Estimated 1RM = weight × (1 + repetitions ÷ 30)
Brzycki formula
Estimated 1RM = weight × 36 ÷ (37 − repetitions)
For example, lifting 100 lb for 5 repetitions gives an Epley estimate of about 116.7 lb and a Brzycki estimate of about 112.5 lb. The average is about 114.6 lb. This is an illustration of the equations, not a promise that you can lift that load once.
Why estimates differ
Rep-max equations work best within limited repetition ranges and may become less reliable for high-repetition sets. Results can also vary by exercise, lifting experience, fatigue, technique, range of motion and individual physiology. Use the same method and conditions when tracking changes.
Frequently asked questions
Is an estimated 1RM the same as my actual maximum?
No. It is a mathematical estimate from a set you completed. Your actual performance may be higher or lower depending on readiness, technique, rest, equipment and other factors.
Which formula is more accurate, Epley or Brzycki?
Neither formula is universally best for every lifter and exercise. Both are widely used estimates; compare them as a range rather than treating one result as exact.
How many reps should I enter?
These equations are commonly used with submaximal sets, especially around 1–10 repetitions. Accuracy can decline as repetitions rise. This calculator limits the input to 12 reps for a more practical estimate.
Can I use my 1RM to plan training percentages?
Yes, many programs use percentages as a starting point. Adjust loads for the target repetitions, how the set feels, technique quality and your coach’s guidance.
Should beginners test their true 1RM?
Beginners usually benefit more from learning technique and building consistency than from testing maximal loads. If a true maximum is tested, it should be done with appropriate supervision, equipment and safety precautions.
Safety: This tool is for training education only. Do not attempt a maximal lift if you are injured, unprepared or unsure of technique. Use safety bars or a competent spotter when appropriate and stop if you experience pain or concerning symptoms.