Strength Training Calculator
What is a One‑Repetition Maximum (1 RM)?
Your 1 RM is the greatest load you can lift for exactly one repetition with proper form, the standard benchmark of maximal muscular strength.
Why estimate 1 RM via submaximal testing?
Direct 1 RM testing is time‑consuming and carries higher injury risk, especially for novices or non-strength athletes. Sub-maximal rep tests (lifting a lighter load to failure) are safer and more practical, yielding a reasonable 1 RM estimate without maximal loads.
Choosing your rep test and prediction formula
Prediction accuracy falls off sharply when using rep tests beyond 10 repetitions; most equations work best for ≤ 10 RM tests. Among common models, the Epley equation shows the smallest error for rep ranges from 2 to 10 RM, making it our primary choice, with Brzycki as an alternative.
How to perform your submaximal rep test
Warm‑up thoroughly (5–10 min light activity plus several rehearsal sets).
Select a load you estimate you can lift for 6–10 reps to failure.
Execute one set to concentric failure (maintaining strict technique).
Record the weight used (kg) and the exact reps completed (1–10).
Rest 3–5 minutes afterwards to recover fully.
How to use the calculator
Enter your lifted weight and reps to failure (1–10).
Select Epley or Brzycki formula.
Calculate to receive:
Estimated 1 RM (rounded to the nearest kilogram)
Load‑for‑% 1 RM table (50 %, 60 %, 70 %, 80 %, 90 %) with intended training purposes (e.g. endurance, hypertrophy, strength).
Use these outputs to calculate precise loads for recovery, endurance, hypertrophy, strength, and maximal‑strength sessions.
Which Formula to Use? Epley vs Brzycki
1. Formula definitions
Epley (1985):
This linear model is easy to compute mentally (“add ~3.33 % of load per rep”) and is commonly used for sub-maximal tests of 2–10 reps.
Brzycki (1993):
This rational model often yields slightly more conservative estimates, particularly useful if you want to err on the side of a lower 1 RM.
2. Comparative accuracy
In a validation study using back‑squat tests, Epley predictions most closely matched actual 1 RM values when rep tests were 3 RM, whereas Brzycki estimates were more accurate for 5 RM tests.
For a 10 RM test, both equations produce identical 1 RM values, so either formula is acceptable at that rep range.
3. Practical guidance
If you plan a low‑rep test (e.g. 3–5 RM), use Epley for 3 RM or Brzycki for 5 RM to maximise accuracy.
For moderate‑rep tests (6–10 RM), Epley is simpler to calculate and just as valid.
Use Brzycki if you prefer a slightly more conservative 1 RM estimate—this can reduce injury risk when programming heavy loads.
Choose the formula that best matches your test protocol and comfort with computation; both will give you a solid foundation for prescribing training loads.