One Rep Max Calculator
A one rep max calculator estimates the maximum weight you can lift for a single repetition of any exercise — without requiring you to actually attempt a dangerous max effort. Enter the weight you lifted and how many reps you completed, and the calculator instantly gives you your estimated 1RM along with a full training load table broken down by percentage. Whether you’re a beginner tracking early strength gains or an experienced lifter planning your next training block, knowing your 1RM helps you train smarter with precise, goal-based loads.
Estimate your 1RM using Epley, Brzycki & Lombardi — evidence-based formulas
Lift Details
Most accurate at 1–10 reps. Less reliable above 12.
Formula
Your Estimated 1 Rep Max
| % 1RM | Weight (kg) | Rep Range | Training Zone |
|---|
What Is a One Rep Max?
Your one rep max (1RM) is the heaviest weight you can lift for exactly one complete repetition with proper form. It is the gold standard for measuring absolute strength and is widely used in powerlifting, Olympic weightlifting, and general strength training. In practice, most lifters never test their true 1RM directly — instead, they use a 1RM calculator to estimate it safely from a sub-maximal effort, such as a set of 5 or 8 reps.
How to Use This Calculator
- Enter the weight you lifted — in kg or lb.
- Enter the number of reps you completed in that set.
- Choose a formula — Epley is selected by default as the most widely used.
- Hit Calculate 1RM to see your estimated max and full training load table.
For the most accurate result, use a weight you can lift for 3–10 reps taken close to failure. Very high rep sets (15+) reduce accuracy across all formulas.
Which Formula Should You Use?
This max lift calculator offers three evidence-based formulas:
| Formula | Best For | Equation |
|---|---|---|
| Epley (1985) | All rep ranges — default | w × (1 + r ÷ 30) |
| Brzycki (1993) | Low reps (1–10), powerlifting | w ÷ (1.0278 − 0.0278 × r) |
| Lombardi (1989) | Moderate reps, higher estimate | w × r^0.10 |
For most people, Epley produces reliable results and is the industry standard. If you compete in powerlifting or primarily work in low rep ranges, Brzycki tends to be more precise. All three results are always shown side by side so you can compare.
How to Calculate One Rep Max Manually
If you prefer to calculate by hand, the Epley formula is the simplest:
1RM = Weight × (1 + Reps ÷ 30)
For example — if you bench pressed 80 kg for 8 reps:
1RM = 80 × (1 + 8 ÷ 30) = 80 × 1.267 = ~101 kg
Training Load Table — How to Use Your 1RM
Once you know your estimated 1RM, you can prescribe training loads as a percentage of that number. This is how coaches and athletes structure every type of strength programme:
| % of 1RM | Rep Range | Training Goal |
|---|---|---|
| 90–100% | 1–3 reps | Maximum strength |
| 75–85% | 5–8 reps | Strength & hypertrophy |
| 65–75% | 8–12 reps | Muscle hypertrophy |
| 50–65% | 12–20 reps | Muscular endurance |
The calculator generates this table automatically based on your result.
Frequently Asked Questions
How accurate is a 1RM calculator?
For sets of 3–10 reps taken close to failure, estimated 1RM is typically within 5% of actual maximal strength. Accuracy drops as rep count rises above 10–12.
Which exercises can I use this for?
Any barbell or machine compound lift — bench press, squat, deadlift, overhead press, row. Less reliable for isolation exercises where fatigue patterns differ significantly.
Should I actually attempt my 1RM?
Only with an experienced spotter, a proper warm-up, and good technique. For most training purposes, the estimated value from this calculator is sufficient.
Buttomline
Tracking your one rep max over time is one of the clearest indicators of strength progress. Use this calculator regularly — after completing a strong working set — to monitor how your max lifts are trending without the injury risk of frequent true max attempts. Save or download your result after each calculation to keep a simple record of your strength over time.