How it works
Epley: 1RM = weight × (1 + reps ÷ 30); Brzycki: 1RM = weight × 36 ÷ (37 − reps)
This page keeps the calculation centered on one relationship: Epley: 1RM = weight × (1 + reps ÷ 30); Brzycki: 1RM = weight × 36 ÷ (37 − reps). Inputs are normalized before the final display, which keeps mile, kilometer, pace, speed, or zone outputs from drifting because of rounding. Use the number as a consistent model output, then layer in terrain, weather, recovery, and race execution. Keep the fixed reference values in view: 1985, 1, 30, 100 kg, 5, 100, 1.1667, 116.7 kg.
Sources
- Epley formula Epley B. Poundage Chart. Boyd Epley Workout. Lincoln, NE: Body Enterprises, 1985 — 1RM = w·(1 + reps/30).
- Brzycki formula Brzycki M. Strength testing — predicting a one-rep max from reps to fatigue. JOPERD. 1993;64(1):88–90 — 1RM = w·36/(37 − reps).
- Accuracy range Rep-max prediction equations are most accurate at low reps (≈1–10) and diverge at higher reps; estimates from very high-rep sets are unreliable.
FAQ
When should I use the one rep max calculator?
Use it when you want a fast planning number before a run, race, workout, or gear decision. It gives you a consistent estimate without asking you to create an account. Keep the fixed reference values in view: 1, 30, 36, 37, 100 kg, 5, 113–117 kg.
What inputs matter most?
The best result comes from honest, current inputs. Recent race times, realistic body measurements, accurate workout data, and the correct unit setting matter more than perfect formatting. Keep the fixed reference values in view: 5.
How should I read the result?
Treat the output as a planning reference, not a promise. Use it to compare options, set a target range, or sanity-check your watch data before making the final call. Keep the fixed reference values in view: 3–6, 12, 1.
Does this work in miles and kilometers?
Yes. PacerRunning is written for US runners first, so miles are easy to use, but metric conversions are kept alongside them where the tool needs both views. Keep the fixed reference values in view: 1.
Why might my real-world result differ?
Terrain, wind, heat, sleep, fueling, training fatigue, and measurement error can all move the real outcome away from the estimate. The One Rep Max one rep max calculator cannot see those details. Keep the fixed reference values in view: 85–95%, 1, 70–85%.
Can beginners use it?
Yes. You do not need advanced training knowledge. Enter the numbers you know, read the result as a guide, and keep your effort comfortable when you are unsure.
One Rep Max Calculator results are estimates from the entered data and the cited method. They are useful for planning and comparison, but they are not a diagnosis, prescription, guaranteed race result, or substitute for a coach or clinician.