Estimate the maximum weight you can lift for a single repetition based on your current performance.
Accuracy is highest when reps are between 1 and 10.
Your One Repetition Maximum (1RM) is the heaviest weight you can lift for a single rep with proper form. It's a key benchmark for tracking strength progress.
Enter your weight and reps (1-10) to see your estimated one rep max and training zones.
A one rep max (1RM) calculator answers the question every lifter asks at some point: "How much weight can I actually lift for a single, all‑out rep – without having to test it and risk injury?"
Your one rep max is the maximum amount of weight you can lift for exactly one repetition of a given exercise. Testing your true 1RM is risky – heavy loads increase injury risk and require days to recover from. This calculator estimates your maximum based on a submaximal set (lifting a weight you can handle for 3‑10 reps).
The most famous formula is the Epley formula, but there are others like Brzycki, Lombardi, and Mayhew. Each gives slightly different results based on population data.
Strength training is more popular than ever. Knowing your 1RM is essential for following periodized programs like 5/3/1 or Starting Strength, allowing you to set precise training loads without the risk of "ego‑lifting."
Each formula does the same job differently. For best results, use a weight you can lift for 2-6 reps.
| Formula | Equation (Weight × Reps) | Example (200 lbs × 5) |
|---|---|---|
| Epley | Weight × (1 + reps/30) | 233 lbs |
| Brzycki | Weight × (36 / (37 – reps)) | 225 lbs |
| Lombardi | Weight × (reps^0.10) | 235 lbs |
| O’Conner | Weight × (1 + reps/40) | 225 lbs |
Once you know your estimated 1RM, you can calculate the exact weights for different training goals. This is the foundation of scientific program design.
Strength / Power
85‑95% of 1RM • 1‑5 Reps
Hypertrophy (Growth)
67‑85% of 1RM • 6‑12 Reps
Endurance
<67% of 1RM • 12+ Reps
Warm up thoroughly with light weight
Choose a weight you can lift for 3‑6 reps
Perform as many clean reps as possible
Stop immediately if form breaks
Plug weight and reps into the calculator
Your relative strength (1RM ÷ Body Weight) is the best way to compare your progress across different weight classes.
| Body Weight | Novice | Intermediate | Advanced |
|---|---|---|---|
| 150 lbs | 120 | 185 | 250 |
| 180 lbs | 145 | 220 | 300 |
| 200 lbs | 160 | 245 | 330 |
| Body Weight | Novice | Intermediate | Advanced |
|---|---|---|---|
| 120 lbs | 55 | 85 | 115 |
| 140 lbs | 65 | 100 | 135 |
| 160 lbs | 75 | 115 | 155 |
Source: Strength Level / ExRx.net
Avoid these pitfalls to ensure your training weights are accurate and safe.
| Mistake | Why It's Wrong |
|---|---|
| Testing with high reps (10+) | Formulas lose accuracy above 10 reps. Use 2‑6 reps for the best results. |
| Poor form / Cheating reps | The calculator assumes clean reps. Bouncing or momentum gives an inflated, risky estimate. |
| Not going to failure | If you stop with reps left in the tank, the estimate will be lower than your true potential. |
| Testing too often | 1RM changes slowly. Test every 8‑12 weeks; focus on training in between. |
A 1RM calculator is the safest, smartest way to know your strength without risking injury. It turns a heavy set into a number you can use to program your training and crush your goals.
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