Estimate your one-repetition maximum (1RM) for strength training using multiple validated formulas. Compare results from Epley, Brzycki, Lombardi, and Mayhew methods.
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🏆 Epley Formula
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Weight × (1 + Reps / 30)
📐 Brzycki Formula
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Weight × 36 / (37 − Reps)
📊 Lombardi Formula
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Weight × Reps0.10
📈 Mayhew Formula
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100 × W / (52.2 + 41.9 × e−0.055×R)
⭐ Average 1RM
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Mean of all four formulas
💪 Estimated Max
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Your approximate 1RM range
📝 Formula Calculations
Real-World One Rep Max Examples
🏋️ Bench Press: 185 lbs × 8 Reps
A lifter completes 8 reps with 185 lbs on the bench press. What is their estimated 1RM?
Epley: 185 × (1 + 8/30) = 229 lbs
Brzycki: 185 × 36/(37−8) = 230 lbs
Lombardi: 185 × 80.10 = 218 lbs
Mayhew: 100×185/(52.2+41.9×e−0.44) = 228 lbs
Average 1RM ≈ 226 lbs — a realistic max for an intermediate lifter.
💪 Squat: 225 lbs × 5 Reps
An experienced lifter squats 225 lbs for 5 reps. What's the estimated maximum?
Epley: 225 × (1 + 5/30) = 263 lbs
Brzycki: 225 × 36/(37−5) = 253 lbs
Lombardi: 225 × 50.10 = 262 lbs
Mayhew: 100×225/(52.2+41.9×e−0.275) = 253 lbs
Average 1RM ≈ 258 lbs — a solid intermediate squat.
🎯 Deadlift: 315 lbs × 3 Reps
A strength athlete pulls 315 lbs for 3 reps. What's their estimated max?
Epley: 315 × (1 + 3/30) = 347 lbs
Brzycki: 315 × 36/(37−3) = 333 lbs
Lombardi: 315 × 30.10 = 351 lbs
Mayhew: 100×315/(52.2+41.9×e−0.165) = 335 lbs
Average 1RM ≈ 342 lbs — an advanced level deadlift.
One Rep Max Formulas Explained
1RM = W × (1 + R / 30)
Epley Formula — Developed by Boyd Epley, this is one of the most widely used 1RM equations. It tends to be more accurate for rep ranges between 2–15.
1RM = W × 36 / (37 − R)
Brzycki Formula — Created by Matt Brzycki, this formula is popular in academic settings and tends to be slightly more conservative for higher rep ranges.
1RM = W × R0.10
Lombardi Formula — Developed by V. Lombardi, this formula uses a power function and tends to predict higher 1RM values at low rep ranges.
1RM = 100W / (52.2 + 41.9e−0.055R)
Mayhew Formula — Based on a study by Mayhew et al., this uses an exponential decay model and is considered very accurate for the bench press.
🔄 Formula Comparison
At low reps (1–5), all formulas give similar results. At higher reps (10+), Epley and Lombardi tend to predict higher values than Brzycki and Mayhew. Use all four for the most comprehensive estimate.
🎯 Best Rep Range
For the most accurate 1RM estimation, use a weight you can lift for 3–10 reps with proper form. Testing with more than 10 reps increases estimation error significantly.
⚠️ Exercise Variability
Your 1RM varies by exercise. Most lifters have a higher deadlift 1RM than bench press 1RM due to muscle group recruitment. Calculate each major lift separately for accurate programming.
🏆
4 Proven Formulas
Compare results from Epley, Brzycki, Lombardi, and Mayhew — the four most validated 1RM estimation equations in strength science.
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Accurate Training Zones
Use your estimated 1RM to calculate proper training percentages for strength, hypertrophy, and endurance phases.
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Visual Comparison
See all four formula results side-by-side with an average estimate to help you choose the right training weight.
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Science-Based
All formulas are peer-reviewed and validated in exercise science research for reliable strength assessment.
Your one-repetition maximum (1RM) is the maximum amount of weight you can lift for a single repetition of a given exercise with proper form. It is the gold standard for measuring absolute strength and is used by athletes, coaches, and strength trainers worldwide to design effective training programs.
Testing your actual 1RM by lifting maximal weight carries inherent injury risk, especially for beginners. That's why estimated 1RM calculators are widely used — they predict your maximum from a submaximal set of 3–10 reps, allowing you to assess strength safely.
Why Calculate Your 1RM?
Knowing your estimated 1RM helps you train more effectively by allowing you to calculate the right weights for specific training goals:
💪 Strength (85–100% 1RM)
Low reps (1–5) with heavy weight for maximal strength gains. Use 85–100% of your estimated 1RM for 1–5 reps per set.
📈 Hypertrophy (67–85% 1RM)
Moderate reps (6–12) for muscle growth. Train at 67–85% of your 1RM for optimal hypertrophy stimulus.
🔋 Endurance (50–67% 1RM)
High reps (12–20+) to build muscular endurance. Use 50–67% of your 1RM and focus on volume over intensity.
📊 Power (80–90% 1RM)
Explosive reps (1–3) at 80–90% 1RM for power development. Focus on bar speed rather than time under tension.
How to Use This Calculator
Using the One Rep Max Calculator is straightforward. Follow these steps to get an accurate estimate of your maximum lifting capacity:
Select an exercise — Choose a compound lift like bench press, squat, or deadlift for the most reliable results.
Warm up properly — Perform 2–3 warm-up sets before your working set to prepare your muscles and nervous system.
Choose a challenging weight — Pick a weight you can lift for 3–10 reps maximum with good form. Avoid going to absolute failure.
Enter the details — Input the weight you lifted and the number of reps you completed in the calculator above.
Compare the results — Review all four formula estimates. The average provides a reliable 1RM estimate for programming.
💡 Tip
For the most accurate results, use a weight you can complete with one or two reps left in the tank (RPE 8–9). Record your results for each major lift separately.
Frequently Asked Questions
❓ Which 1RM formula is the most accurate?
The Epley formula is the most widely validated and is generally considered the most accurate across a broad range of rep schemes (2–15 reps). However, accuracy varies by exercise — the Mayhew formula was specifically developed for the bench press and may be more accurate for that lift. We recommend using the average of all four formulas for the most reliable estimate.
❓ What is the best rep range for estimating 1RM?
The ideal rep range is 3–10 reps. Testing with fewer than 3 reps doesn't provide enough data for accurate estimation, and testing with more than 10 reps introduces significant error because the relationship between reps and max weight becomes nonlinear. For the most reliable results, use a weight you can lift for about 5–8 reps.
❓ Can I test my actual 1RM instead of using an estimate?
Yes, but it carries risks. Actual 1RM testing requires proper technique, a spotter, and significant warm-up. It's best suited for experienced lifters who have mastered form. Beginners and intermediates should use estimated 1RM calculations for at least 3–6 months of consistent training before attempting a real max. Always prioritize safety and proper form over lifting the heaviest weight possible.
❓ Does my 1RM vary between different exercises?
Absolutely. Your 1RM is specific to each exercise. For most lifters, the deadlift 1RM is the highest (recruiting the largest muscle groups), followed by the squat, then bench press, then overhead press. Always calculate separate 1RM estimates for each major compound lift. Never assume your bench press 1RM equals your squat 1RM — they are very different strength measures.
❓ How often should I recalculate my 1RM?
Recalculate your estimated 1RM every 4–8 weeks as your strength improves. Many training programs use 1RM percentages to set working weights, so keeping your estimate up to date ensures you're training at the right intensity. If you complete a training cycle and notice your reps at a given weight have increased significantly, it's time to re-estimate.
❓ Can I use this for machine exercises too?
Yes, the formulas work for any resistance training exercise, including machines, cables, and dumbbells. However, the formulas were originally validated on compound barbell lifts (bench press, squat, deadlift). For machine exercises or isolation movements, treat the estimates as approximate guides rather than precise measurements. The rep-to-max relationship on machines may differ slightly from free weight exercises.
⚠️ Safety Warning: This calculator provides estimates only. Actual 1RM testing carries risk of injury. Always use proper form, warm up adequately, and have a spotter when attempting heavy lifts. Consult a qualified strength and conditioning professional before starting any new training program. Never sacrifice form to lift heavier weight.