One-Rep Max (1RM) Calculator – Estimate Your Max Lift
Enter the weight and reps from a recent hard set to estimate the heaviest single rep you could lift.
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- lb & kg supported
Calculate Your 1RM
Use a set taken close to failure. Estimates are most reliable at 10 reps or fewer.
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Enter a weight and rep count, then select Calculate My 1RM to see your estimated max and training weights.
Your Estimated 1RM
Average of seven common formulas. Treat it as a starting estimate, not a guarantee.
Training weights by % of 1RM
| % of 1RM | Weight | Typical reps |
|---|
Result by formula
| Formula | Estimated 1RM |
|---|
Estimates only, not a guarantee of what you can lift. See the safety note below.
What Is a One-Rep Max (1RM)?
Your one-rep max (1RM) is the heaviest weight you can lift for a single repetition of an exercise with proper form. It's the standard way to measure maximal strength and to set training loads as a percentage of your best lift.
Testing a true 1RM can be tiring and carries more injury risk than lighter sets, so many lifters estimate it instead: perform a hard set of several reps, then use a formula to predict the single-rep maximum.
How Is 1RM Calculated?
A 1RM calculator estimates your max from the weight (w) and repetitions (r) of a submaximal set. This calculator runs seven published formulas and shows their average, because no single formula is best for every lift or every person.
| Formula | Equation |
|---|---|
| Epley | w × (1 + r ÷ 30) |
| Brzycki | w × 36 ÷ (37 − r) |
| Lander | 100 × w ÷ (101.3 − 2.67123 × r) |
| Lombardi | w × r0.10 |
| Mayhew | 100 × w ÷ (52.2 + 41.9 × e−0.055 × r) |
| O'Conner | w × (1 + 0.025 × r) |
| Wathan | 100 × w ÷ (48.8 + 53.8 × e−0.075 × r) |
If you completed exactly one rep, the calculator uses that weight directly as your 1RM. Accuracy generally falls as reps rise, so sets of 10 reps or fewer give the most reliable estimates.
1RM Percentage Chart
Training percentages tell you how heavy to lift relative to your max. Lower percentages allow more reps; higher percentages allow fewer.
| % of 1RM | Typical reps | Common training focus |
|---|---|---|
| 95 – 100% | 1 – 2 | Maximal strength, testing |
| 85 – 90% | 4 – 6 | Strength |
| 75 – 80% | 8 – 10 | Strength and muscle size |
| 65 – 70% | 12 – 15 | Muscle size and endurance |
| 50 – 60% | 20 or more | Muscular endurance, technique, warm-ups |
These rep ranges are general guidelines. Individual results vary by exercise, training experience, and fatigue.
How to Use Your 1RM in Training
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Warm up, then perform a hard set
After a thorough warm-up, lift a challenging weight for 3 to 8 reps, stopping when your form would break down.
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Enter the weight and reps
Use the actual weight and the number of clean reps completed. Estimates are best from sets of 10 reps or fewer.
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Plan your sessions by percentage
Use the training-weights table to choose loads for your goal, then update your estimate every few weeks as you get stronger.
Frequently Asked Questions
It is the heaviest weight you can lift for one repetition of an exercise with proper form.
It gives a reasonable estimate, especially from sets of 10 reps or fewer. Accuracy drops as reps increase and varies by exercise and individual.
No single formula is best for everyone. Epley and Brzycki are the most widely used, which is why this calculator shows several formulas and their average.
Between 3 and 8 reps is a common sweet spot. Sets of 10 reps or fewer generally give more reliable estimates than higher-rep sets.
A true max attempt carries more risk than lighter sets. Warm up thoroughly, use a spotter or safety bars, and consider estimating from a submaximal set instead.
Yes. The formulas work for any barbell or machine lift, though estimates tend to be most reliable for compound lifts like the bench press, squat, and deadlift.
Every 4 to 8 weeks is common, or whenever you notice you're lifting noticeably more weight for the same reps.
No. It provides general estimates for informational purposes and does not replace guidance from a qualified coach or healthcare professional.
Our Methodology
- Calculation method
- Average of seven published 1RM prediction formulas
- Rep range
- 1 – 30 reps (most reliable at 10 or fewer)
- Reviewed by
- [Qualified Reviewer Name — Replace Before Publishing]
- Written by
- [Author Name — Replace Before Publishing]
- Last reviewed
- [Date — Replace Before Publishing]
Sources
- Peer-reviewed research comparing 1RM prediction equations [Add citation]
- Strength and conditioning organization guidance [Add citation]
Replace the source placeholders above with the references used to establish this calculator's methodology before publishing.
Safety Disclaimer
This calculator provides estimated values for general informational purposes. It cannot guarantee what you can safely lift. Always warm up, use proper technique, and lift with a spotter or safety equipment when attempting heavy weights.
If you have an injury, a medical condition, or are new to strength training, please consult a qualified coach or healthcare professional first.