One Rep Max Calculator (1RM Calculator)
Free One Rep Max (1RM) calculator. Enter the weight and reps (1–12) you lifted to estimate your 1RM using the Epley, Brzycki, and Lombardi formulas, plus a %1RM weight chart.
How the 3 Estimation Formulas Differ
| Formula | Characteristics |
|---|---|
| Epley Formula | Published by Boyd Epley in 1985, this is the most widely used formula. It's a simple linear equation, 1RM = weight × (1 + reps ÷ 30), which tends to run slightly high at higher rep counts. |
| Brzycki Formula | Published by Matt Brzycki in 1993. The formula is 1RM = weight × 36 ÷ (37 − reps), and it's well regarded for its accuracy in the mid rep range around 10 reps. |
| Lombardi Formula | This formula uses a gentler weighting, 1RM = weight × reps^0.10, and tends to produce more conservative values than the Epley formula at higher rep counts. |
Typical Rep Count by %1RM
| %1RM | Typical rep count |
|---|---|
| 100% | 1 rep |
| 95% | 2 reps |
| 93% | 3 reps |
| 90% | 4 reps |
| 87% | 5 reps |
| 85% | 6 reps |
| 83% | 7 reps |
| 80% | 8 reps |
| 77% | 9 reps |
| 75% | 10 reps |
| 70% | 11 reps |
| 67% | 12 reps |
These are general guidelines widely referenced in training science, and individual results can vary. Even at the same %1RM, the number of reps you can manage may shift depending on your muscle fiber composition and the exercise itself.
What Is a One Rep Max (1RM) Calculation?
Your One Rep Max (1RM) is the heaviest weight you can lift for a single rep with correct form. It's commonly used as the basis for setting training weights (for example, bench pressing at 70% of your 1RM for 8 reps × 3 sets), but actually attempting a true 1RM carries a real risk of injury, so it isn't something you should test often.
This tool works backward from a weight and rep count you lifted with a bit of a buffer (roughly 2–12 reps) to estimate your theoretical 1RM. It shows results from three formulas commonly used in practice — Epley, Brzycki, and Lombardi — side by side, giving you a range rather than a single definitive number. All calculations run entirely in your browser, so the weight and rep count you enter are never sent to a server.
How to Calculate Your 1RM
- Enter the weight from a near‑failure set Enter a weight from a set where you had about 1–2 reps left before failure, while still keeping good form. You can choose either kg or lb as the unit.
- Enter the number of reps completed Enter a value between 1 and 12 reps. Estimation error grows with higher rep counts, so if possible, it's best to measure with a set of 5 reps or fewer.
- Check your estimated 1RM and the weight chart The average of the three formulas is shown as the primary estimate, alongside a weight chart covering 50%–100% of your %1RM.
Tips for getting more out of it
- You don't need to actually attempt your true 1RM. Working backward from a set with a bit of buffer (around 3–5 reps) gives you an estimate that's accurate enough for practical training purposes.
- How well the formulas fit can vary by exercise. They tend to be more accurate for compound lifts that use large muscle groups, such as the bench press, squat, and deadlift, and less accurate for single‑joint exercises like arm curls.
- The estimate depends on how close to true failure that set actually was, even at the same weight and rep count. If you still had a lot left in reserve, the estimated 1RM will come out lower than your true max.
- You can use the %1RM values from the chart directly when setting training intensity. A common guideline is to target 65–85% for muscle growth and 85% or higher for strength gains.
- If you'd also like to track your body composition and calorie needs, check out our Lean Body Mass (LBM) Calculator and Target Calorie / TDEE Calculator.
Ways to Use 1RM Calculations
Setting training weights for a program
When following a program like "8 reps × 3 sets at 70% of 1RM," you can calculate your target weight without having to test your true max.
Tracking and comparing progress
Instead of testing your true 1RM every time, you can log your estimated 1RM from your regular sets to track long‑term progress.
Setting goals for powerlifting competition
Adding up your estimated 1RM for the bench press, squat, and deadlift can help you set a target for your total.
Adjusting weight after returning from injury
Right after returning from injury, you can estimate your 1RM from lighter sets without pushing to failure, giving you a safe starting point to build back up from.
One Rep Max Terminology
- 1RM
- Short for One Rep Max, this is the heaviest weight you can lift for a single rep with correct form. It's used as a benchmark for setting training intensity.
- %1RM
- A percentage of your 1RM. Phrases like "80% of 1RM" are used to set training weights based on your goal, whether that's strength, muscle growth, or endurance.
- Number of reps
- Also referred to as RM (Repetition Maximum), this is the number of consecutive reps you can complete at a given weight. "5RM" means the heaviest weight you can lift for exactly 5 reps.
- Epley Formula
- A 1RM estimation formula published by Boyd Epley in 1985. It's a simple linear equation, 1RM = weight × (1 + reps ÷ 30), and remains the most widely used formula today.
- Brzycki Formula
- A 1RM estimation formula published by Matt Brzycki in 1993. The formula is 1RM = weight × 36 ÷ (37 − reps), and it's well regarded for its accuracy in the mid rep range around 10 reps.
Frequently Asked Questions
Side Note — Where Did 1RM Estimation Formulas Come From?
The concept of a 1RM has been used in weightlifting competition for a long time, but it wasn't until Brzycki, Epley, and others published their estimation formulas in the 1980s and 90s that everyday lifters could easily estimate it themselves. Before that, you either had to actually test your max weight or rely on rough rules of thumb.
When the Epley formula was published in 1985, it was widely assumed in sports science that the relationship between reps and weight lifted was essentially linear. The Brzycki formula, by contrast, takes a hyperbolic form with reps in the denominator, and is considered to produce results closer to actual measurements, especially for sets around 10 reps. Because of this difference, it's still common practice today to present multiple formulas side by side rather than relying on just one.
What's interesting is that all of these formulas are designed around the assumption that the set was pushed close to true failure. If you plug in numbers from a set that felt easy, the resulting estimate will come out well above your actual 1RM. Some argue that the accuracy of the result depends less on the formula itself and more on how honestly you judge whether that set was really close to your limit.
In powerlifting competition, by the way, the official record is the combined 1RM total across the bench press, squat, and deadlift. World records are tracked by bodyweight class and age class, and what counts toward the record is the actual heaviest successful attempt out of three tries, not a formula‑based estimate — which sets it apart from the way 1RM is typically estimated in everyday training.