One-Rep Max Calculator

How to use this calculator

1. Choose the lift you’re testing (for example, squat, bench, deadlift, overhead press) and load your bar or machine with a weight you can perform safely for several reps.
2. Perform a set of controlled reps to near technical failure, stopping the set when you feel you only have 1–2 good reps left in the tank.
3. Enter the weight used (in pounds) and the exact number of reps you completed with good form (ideally between 1 and 10).
4. We apply the Epley formula to output an estimated 1RM for that lift.
5. Use the estimated 1RM to set percentages for future work sets (for example, 70%, 80%, or 90% of estimated max).

Inputs explained

Weight lifted

The load you used for the test set, in pounds. Use a weight you can manage with solid technique; do not attempt true maxes without proper safety measures.

Reps completed

The number of clean, full‑range reps performed at that weight before you would have to grind or break form. For best accuracy, keep reps between 1 and 10.

When to use it

• Setting training percentages for strength programs (for example, 5×5, Wendler, or other percentage‑based templates) without frequent 1RM tests.
• Tracking strength changes over time by plugging in rep PRs (for example, new 5‑rep or 8‑rep bests) and comparing estimated 1RMs.
• Estimating safe starting weights when switching programs or returning from a layoff or injury.
• Giving lifters and coaches a common language to discuss progress when true max testing is not feasible.

Tips & cautions

• Keep reps between 1 and 10 for best accuracy; very high‑rep sets (15+ reps) tend to inflate 1RM estimates.
• Use consistent form, range of motion, and tempo when comparing estimates over time, so you’re not mixing apples and oranges.
• Consider cross‑checking with other formulas (Brzycki, Lombardi, etc.) if you want a range rather than a single number.
• Remember that day‑to‑day factors like fatigue, sleep, and nutrition affect performance; treat small changes in estimated 1RM with appropriate caution.
• Less accurate for very high reps, highly trained powerlifters, or very heavy singles; this is a model, not a direct measurement.
• Rep‑based estimates are sensitive to fatigue and technique—fatigue from prior sets or poor form can skew results downward.
• Does not distinguish between different lifts automatically; some lifters find estimates more accurate for certain movements than others.

Worked examples

Deep dive

FAQs

Is this accurate for high reps?

Accuracy drops off as reps climb. For sets above about 10 reps, the formula tends to overestimate true max. For better estimates, test with heavier weights and lower rep counts.

Should I ever test a true 1RM instead?

Estimated 1RMs are great for most training, but occasional true max tests—performed safely with a spotter and proper warm‑up—can validate your estimates and provide specific feedback for powerlifting‑style goals.

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