One-Rep Max (O'Conner) Calculator
Enter weight and reps to estimate your one-rep max.
Result
How to use
- Enter your values in the fields above.
- Press Calculate to see your result instantly.
- Use the Share button to copy a link to your result.
About this calculator
The O'Conner formula estimates a one-rep max (1RM) — the maximum weight a person can lift for a single repetition — from a lighter weight lifted for multiple reps, using 1RM = weight × (1 + 0.025 × reps). It's one of several linear estimation formulas, alongside Epley and Brzycki, each built from different regression data, and it tends to produce slightly more conservative estimates than Epley's formula at higher rep counts.
Strength coaches and lifters use 1RM estimates to set training percentages for programs based on a percentage of max, like 5/3/1 or linear periodization, without needing to actually attempt a maximal, injury-risking single lift. Because true 1RM testing is fatiguing and carries injury risk, especially for untrained lifters, formula-based estimates from a submaximal set are the standard, safer way to track strength progress over time.
Was this helpful?
Popular calculators
Loan Calculator
Monthly payment, total interest and full amortization schedule.
Percentage Calculator
Percent change, percent of, and ratio calculations.
Discount Calculator
Calculate final price, savings, and discount amount.
BMI Calculator
Body mass index from height and weight (metric or imperial).
Age Calculator
Compute your exact age in years, months and days from a birth date.
Compound Interest Calculator
Calculate the final amount and interest earned with compounding.
All Calculators
No calculators found
Comments (0)