One Rep Max Calculator
Estimate your one rep max from any weight and rep count using six proven formulas — including Epley and Brzycki. Get your training percentage table instantly.
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Enter Your Lift
Enter the weight you lifted and the number of reps completed to estimate your one rep max.
Formula Comparison
Estimated 1RM from six validated formulas. Epley is the most commonly used in strength sports.
| Formula | Estimated 1RM |
|---|---|
| Enter values and click Calculate | |
Training Percentages
Based on your Epley 1RM. Use these loads to structure your program.
| % | Weight | ~Reps |
|---|---|---|
| — | ||
Understanding Your 1RM
What is a one rep max?
Your one rep max (1RM) is the maximum load you can lift for a single repetition with proper form. It is the most common measure of absolute strength in powerlifting, weightlifting, and strength and conditioning programs.
Rather than maxing out directly — which carries injury risk — most athletes use a submaximal set (3–6 reps) and plug the numbers into a predictive formula. This calculator uses six validated equations and reports them side by side so you can see how they compare.
- Test with 3–6 reps for the most accurate estimate.
- Above 10 reps, all formulas lose accuracy significantly.
- Epley is the default because it performs well across the widest rep range.
Epley vs Brzycki — which formula should you use?
The Epley formula (1RM = w × (1 + r/30)) is the most widely cited and tends to perform well across the 1–10 rep range. It was introduced in 1985 and remains the industry default.
The Brzycki formula (1RM = w × 36 / (37 − r)) is similarly accurate for 1–10 reps but becomes undefined at 37 reps. It is slightly more conservative — useful if you prefer not to overestimate your max.
- Lander and Mayhew use exponential components and can be more precise at moderate rep counts.
- Lombardi uses a power function and tends to produce lower estimates.
- O'Conner (w × (1 + r/40)) is the most conservative of the six.
Percentage-based training
Once you know your 1RM, you can structure your entire training program around percentages of that number. This is the foundation of most evidence-based strength programs.
- 90–95% — Heavy singles and doubles. Maximal strength development.
- 80–85% — Strength work, 3–5 reps. Core of powerlifting programming.
- 70–80% — Strength-hypertrophy overlap, 5–8 reps.
- 60–70% — Hypertrophy and volume work, 8–15 reps.
- Below 60% — Technique, warm-ups, endurance sets.
Safety tips for 1RM testing
Maximal and near-maximal lifts require extra care. Follow these guidelines to reduce injury risk whether you test directly or use submaximal estimation.
- Warm up thoroughly — work up gradually with 50%, 70%, 85%, 95% before any max attempt.
- Use a spotter or safety equipment — squat racks, safety bars, and a trained spotter are essential for heavy lifts.
- Prefer submaximal testing — a 3–6 rep set close to failure is safer and nearly as accurate as a true max test.
- Rest between attempts — allow 3–5 minutes between heavy sets to ensure full recovery.
- Do not test when fatigued — test early in a training week after a deload or recovery day.
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What is a one rep max (1RM)?
A one rep max (1RM) is the maximum weight you can lift for a single repetition with correct form. It is the standard reference point for strength in powerlifting and strength and conditioning. Knowing your 1RM lets you prescribe training loads precisely as a percentage of your maximum capability.
Which 1RM formula is the most accurate?
The Epley formula is the most widely used and performs consistently well across the 1–10 rep range. Brzycki is similarly accurate and slightly more conservative. For the most reliable estimate, test with a weight you can lift for 3–6 reps. All formulas lose accuracy significantly above 10 reps.
Is 1RM testing safe?
Maximal lifting carries a higher injury risk than submaximal work, especially without proper preparation or a spotter. Using this calculator with a 3–6 rep set is a safer alternative that gives a nearly equivalent estimate. Always warm up thoroughly, use safety equipment, and have an experienced spotter present for heavy attempts.
How do I use training percentages?
Training percentages let you prescribe exact loads based on your 1RM. Heavy strength work (1–3 reps) uses 90–95%. Classic strength training (3–5 reps) uses 80–87%. Hypertrophy work (6–12 reps) uses 65–80%. Endurance and technique work uses 50–65%. The training table in this calculator shows the weight and expected rep count for each percentage level.
How often should I test my 1RM?
Most strength athletes test their 1RM at the end of a training cycle — typically every 8–16 weeks. Testing too frequently increases fatigue and injury risk. Using submaximal rep testing (3–6 reps) to estimate your 1RM with this calculator is a practical way to track progress more regularly without the demands of a true max effort.