1 Rep Max Calculator
Estimate your one rep max (1RM) from any set of 1–30 reps. Compare 7 proven formulas, see your percentage chart, rep max table, training zones, barbell plate loading and strength level – all free and instant.
Enter your lift
Your estimated one rep max
Enter a weight and rep count to begin.
Waiting for input1RM percentage chart
Working weights at each percentage of your one rep max, with the approximate reps you can expect. Tap “Load bar” to see the plates.
Rep max table (1RM to 12RM)
The heaviest weight you could lift for each number of reps, based on the formula you selected.
Formula comparison
Every formula estimates slightly differently. The spread shows how much uncertainty is in any single estimate.
Training zones based on your 1RM
Barbell plate calculator
See which plates to load on each side of the bar.
Strength level check
Compare your estimated 1RM with typical strength standards for your bodyweight.
Saved results
Results are stored only in your browser on this device.
What Is a 1 Rep Max Calculator?
A 1 rep max calculator estimates the maximum weight you could lift for a single repetition of an exercise, without you having to actually attempt that max. Instead of loading the bar to your limit, you enter a weight you lifted and how many clean reps you completed. The calculator then applies a validated formula to predict your one rep max (1RM).
Knowing your 1RM is the foundation of percentage-based programs such as 5/3/1, Starting Strength progressions, Texas Method and most powerlifting and bodybuilding templates. This one rep max calculator also builds your percentage chart, rep max table, training zones and plate loading automatically.
How to Use This One Rep Max Calculator
- Choose kilograms or pounds.
- Enter the weight you lifted in a recent hard set.
- Enter the number of reps you completed with good form (1–30). Results are most accurate between 2 and 10 reps.
- Pick a formula, or leave it on the average of all seven for the most balanced estimate.
- Read your estimated 1RM, then explore the percentage chart, rep max table, training zones and plate calculator below it.
One Rep Max Formulas Explained
There is no single perfect equation. Different formulas were built from different lifters and exercises, which is why this tool shows all of them. In the formulas below, w is the weight lifted and r is the number of reps.
| Formula | Equation | Notes |
|---|---|---|
| Epley | w × (1 + r / 30) | Popular and simple; tends to run slightly high at higher reps. |
| Brzycki | w × 36 / (37 − r) | Very common; best for sets under 10 reps. |
| Lander | 100 × w / (101.3 − 2.67123 × r) | Close to Brzycki for most rep ranges. |
| Lombardi | w × r0.10 | Often gives higher numbers for upper-body lifts. |
| Mayhew | 100 × w / (52.2 + 41.9 × e−0.055 × r) | Developed from bench press data. |
| O'Conner | w × (1 + 0.025 × r) | Simple linear model; usually the most conservative. |
| Wathan | 100 × w / (48.8 + 53.8 × e−0.075 × r) | Exponential model with good mid-range accuracy. |
How to Use Your 1RM in Training
Once you know your one rep max, you can prescribe your training load as a percentage of it:
- 85–100% of 1RM (1–5 reps): maximal strength and neural adaptation.
- 67–85% of 1RM (6–12 reps): muscle growth (hypertrophy) with a balance of load and volume.
- Below 67% of 1RM (12+ reps): muscular endurance, technique work and warm-up sets.
Retest or re-calculate every 4–8 weeks, or whenever you hit a rep PR, so your percentages stay current.
Should You Test a True 1 Rep Max?
Testing a true max carries more injury risk and fatigue than a submaximal set, especially for beginners or on lifts without safety pins or a spotter. A one rep max calculator lets you track progress using sets of 3–8 reps, which are safer and easier to recover from. If you do test a real single, warm up thoroughly, use a spotter or safety arms, and keep technique strict.
Tips for More Accurate 1RM Estimates
- Use a true max-effort set taken close to failure, not a set where you stopped with many reps left.
- Prefer lower rep counts (2–8). Accuracy drops noticeably beyond 10 reps.
- Count only reps with consistent depth, pause and form.
- Use the same exercise variation and equipment each time to compare results fairly.
- Treat the result as a range, not an exact number – compare formulas on the “Formula comparison” tab.
1 Rep Max Calculator FAQ
What is a one rep max (1RM)?
Your one rep max is the heaviest weight you can lift for one complete repetition of an exercise with proper technique. It is the standard measure of maximal strength and the basis for percentage-based training.
How accurate is a 1 rep max calculator?
Estimates are typically within about 5% of a true max for sets of 10 reps or fewer. Accuracy decreases as reps increase, and it varies by exercise, training experience and fatigue. Using the average of several formulas reduces the error from any single equation.
Which 1RM formula is best?
No formula is best for everyone. Epley and Brzycki are the most widely used. For general use, the average of all formulas gives a balanced result, which is why it is the default in this calculator.
Can I use this calculator for squat, bench press and deadlift?
Yes. The formulas work for any barbell or machine lift, including squat, bench press, deadlift, overhead press, rows and leg press. Results are most reliable on compound lifts performed with strict technique.
How many reps should I use to calculate my one rep max?
Between 2 and 8 reps gives the best balance of accuracy and safety. A set of 1 simply returns the weight you lifted, and sets above 10 are less reliable.
How often should I recalculate my 1RM?
Most lifters recalculate every 4 to 8 weeks or after setting a new rep record. Recalculating regularly keeps your training percentages matched to your current strength.
What percentage of 1RM should I train at?
For strength, train at roughly 85–95% for 1–5 reps. For muscle growth, use about 65–85% for 6–12 reps. For endurance and warm-ups, stay below about 65%.
Disclaimer: This one rep max calculator provides estimates for educational purposes only and is not medical or coaching advice. Always warm up, use proper form and safety equipment, and consult a qualified professional before starting or changing a training program.