One Rep Max (1RM) Calculator
Estimate your one-rep max with Epley, Brzycki and Lombardi equations, plus 70–90% training loads.
In short
Estimate your one-rep max with Epley, Brzycki and Lombardi equations, plus 70–90% training loads.
Formula: Epley: 1RM = w × (1 + reps ÷ 30). Brzycki: 1RM = w × 36 ÷ (37 − reps). Lombardi: 1RM = w × reps^0.10. A single completed repetition is reported as the lifted weight.
What this calculator does
Estimate your one-rep max with Epley, Brzycki and Lombardi equations, plus 70–90% training loads. Formula, worked example, sources, FAQs and limitations included.
You enter weight lifted, repetitions completed to failure, prediction equation and weight unit (label only), and the one rep max (1rm) calculator shows the answer along with the working, so you can check it or try other numbers.
The page shows the formula, a numeric worked example, and the assumptions that affect this health & fitness calculation.
Inputs and what they mean
- Weight lifted
- — number value.
- Repetitions completed to failure
- — Prediction is most reliable at 10 reps or fewer..
- Prediction equation
- — choice value.
- Weight unit (label only)
- — choice value.
How to use it
- Enter each value in the unit shown next to the box (use the unit converter first if your numbers are in other units).
- Check the breakdown to see every intermediate step.
- Read the limitations before relying on the result.
Formula
Source: LeSuer et al. (1997), J Strength Cond Res 11(4):211–213 — compared these equations against measured 1RM.
LeSuer et al. found all equations underestimated deadlift 1RM; accuracy differs by lift and person.
Epley: 1RM = w × (1 + reps ÷ 30). Brzycki: 1RM = w × 36 ÷ (37 − reps). Lombardi: 1RM = w × reps^0.10. A single completed repetition is reported as the lifted weight.
Inputs used: Weight lifted, Repetitions completed to failure, Prediction equation, Weight unit (label only).
Worked example
100 kg for 5 reps (Epley)
- 5 ÷ 30 = 0.1667.
- 100 × 1.1667 ≈ 116.67 kg.
- Brzycki gives 112.5 kg; Lombardi ≈ 117.46 kg.
Reading the result
The headline figure is the main answer. Any breakdown underneath shows the parts that make it up, so you can check the working and see what changes when you adjust an input.
Limitations and assumptions
- Population prediction equations; individual error can be large, especially above 10 reps.
- Not a training prescription or medical clearance.
- For general fitness education only — not medical advice, diagnosis or a training prescription. Prediction equations are population estimates; speak with a qualified professional before changing exercise or diet, especially with a health condition.
- The result depends on the values you enter for this one rep max (1rm) calculator; it does not supply missing rates, rules, prices, dates, or assumptions for you.
Reference: Journal of Strength and Conditioning Research
Last reviewed:
Common questions
Which formula is most accurate?
None is best for everyone. LeSuer et al. (1997) found differences by lift, and all underestimated the deadlift. Compare the three estimates shown.
Should I test my true 1RM?
Maximal testing carries injury risk. Estimates let you plan loads without a true maximal attempt; seek qualified coaching for max testing.
Why limit reps to 20?
Prediction error grows with reps, and Brzycki becomes undefined near 37 reps.
How do I use the One Rep Max (1RM) Calculator?
Enter the required values for Weight lifted, Repetitions completed to failure, Prediction equation, Weight unit (label only). The calculator applies the formula on this page and shows the main result with any supporting breakdown so you can check the arithmetic.
What formula does the One Rep Max (1RM) Calculator use?
Epley: 1RM = w × (1 + reps ÷ 30). Brzycki: 1RM = w × 36 ÷ (37 − reps). Lombardi: 1RM = w × reps^0.10. A single completed repetition is reported as the lifted weight. The visible formula section above lists the calculation path and the edge cases the page handles, so the result can be checked without relying on the form alone.
Can the One Rep Max (1RM) Calculator be used for exact decisions?
Use it as a calculation aid, not as a substitute for checking the underlying rule, contract, policy, or professional advice that applies to your situation. When a result depends on local rules, personal details, prices, or dates, enter those values yourself and confirm them before acting.
Sources
Method based on Journal of Strength and Conditioning Research.
Cite this page
Free Calculator. (2026, November 3). One Rep Max (1RM) Calculator. https://freecalculator.tech/tools/one-rep-max-calculator
"One Rep Max (1RM) Calculator." Free Calculator, 3 Nov. 2026, https://freecalculator.tech/tools/one-rep-max-calculator.
One Rep Max (1RM) Calculator — Free Calculator, https://freecalculator.tech/tools/one-rep-max-calculator
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