Enter the weight you lifted and how many reps you performed to instantly estimate your one‑rep max using four proven formulas (Epley, Brzycki, Lombardi, and O’Conner). The calculator also gives a multi‑formula average and supports both kilograms and pounds.
Free 1RM calculator – no sign‑up
Calculate Your One Rep Max in Seconds
Estimate your maximum lift without maxing out. Enter the weight you lifted and how many reps you completed — the tool instantly calculates your 1RM using Epley, Brzycki, Lombardi, and more formulas. All free, private, and instant.
Know Your Max Without Maxing Out
Testing your true one‑rep max can be risky and exhausting. Our One Rep Max Calculator uses proven formulas to estimate your maximum lift from a sub‑maximal set. Just enter the weight you lifted and how many reps you completed — the tool instantly gives you your estimated 1RM, along with results from multiple methods so you can pick the most reliable one for your training. Whether you’re programming for strength, setting benchmarks, or tracking progress, this calculator keeps you safe while giving you the numbers you need. All calculations are private and done right in your browser.
What Is a One Rep Max Calculator?
A one rep max (1RM) calculator is a free online tool that estimates the maximum amount of weight you can lift for a single repetition of an exercise. Instead of attempting a risky all‑out lift, you input a sub‑maximal weight and the number of repetitions you can perform with that weight. The calculator applies one of several validated formulas — such as Epley, Brzycki, Lombardi, or Mayhew — to predict your 1RM. It can also show a percentage‑based loading chart, helping you determine how much weight to use for a given rep range. It’s a staple for powerlifters, bodybuilders, and anyone doing structured strength training.
How to Use the One Rep Max Calculator
Enter the Weight You Lifted
Provide the amount of weight you used for a particular exercise — it can be in pounds or kilograms.
Enter the Number of Reps
Type in the maximum number of reps you completed with that weight, ideally to failure or near‑failure (≤10 reps best).
View Your Estimated 1RM & Percentages
Instantly see your predicted max and a table showing what weights to use for various rep schemes — no sign‑up required.
How the 1RM Calculator Estimates Your Max
The calculator uses several well‑known formulas. The **Epley** formula is 1RM = weight × (1 + reps/30). **Brzycki**: 1RM = weight × (36 / (37 – reps)). **Lombardi**: 1RM = weight × reps^0.10. **O’Conner**: 1RM = weight × (1 + reps/40). The tool displays the average and the individual results, and also computes percentage‑based training loads (e.g., 80% of 1RM, 90% of 1RM) for common rep ranges. All calculations run locally in your browser, so your training data stays private.
Core 1RM Formulas
Epley: 1RM = W × (1 + R/30)
Brzycki: 1RM = W × 36 / (37 – R)
Lombardi: 1RM = W × R^0.10
W = weight lifted, R = number of repetitions performed. Most formulas are most accurate for ≤10 reps.
Key Features of This One Rep Max Calculator
Multiple Formula Estimates
See your 1RM from Epley, Brzycki, Lombardi, O’Conner, and Mayhew — all at once.
Percentage Loading Chart
Instantly get a table of weights for 50% to 100% of your 1RM, tailored to your strength level.
Units in lbs or kg
Enter weight in either unit; the calculator uses the same unit for all outputs so you can program your lifts easily.
Private & Secure
Your training data stays on your device. Nothing is ever uploaded or shared.
Benefits of Knowing Your One Rep Max
- ✅ Safer training – avoid the injury risk of a true 1RM test while still getting an accurate estimate
- ✅ Precise programming – set working weights for strength, hypertrophy, and power phases with confidence
- ✅ Track progress – as your estimated 1RM goes up, you know you’re getting stronger
- ✅ Compare lifts – use the same method for bench press, squat, deadlift, or any exercise
- ✅ Set goals – pick a target 1RM and work backward to determine the reps and weight needed to achieve it
Understanding the 1RM Formulas
Epley Formula
1RM = weight × (1 + reps/30). Simple and widely used in fitness apps. Works best for reps ≤10.
Brzycki Formula
1RM = weight × 36 / (37 – reps). Tends to be slightly more conservative than Epley for lower reps.
Lombardi & Others
Lombardi: 1RM = weight × reps^0.10. O’Conner: weight × (1 + reps/40). Mayhew: weight × (100 / (52.2 + (41.9 × e^(-0.055 × reps)))). The calculator shows all so you can take an average.
How to Use the Percentage Loading Chart
Once you have your estimated 1RM, the calculator generates a full table showing the weight you should use for 50%, 55%, 60% … up to 95% of your max. This is invaluable for periodized programs like 5/3/1, Westside, or any plan that prescribes loads as a percentage of 1RM. You can see exactly what to load on the bar for your main sets and assistance work, eliminating guesswork from your training.
Safety and Limitations of Estimated 1RM
Best for ≤10 Reps
These formulas become less accurate with very high reps (15+). For strength estimation, use a set you can perform to failure within 1‑10 reps.
Not a True Max
An estimated 1RM is just that — an estimate. Actual performance may vary due to fatigue, technique, and daily readiness. Never attempt a calculated 1RM without proper warm‑up and spotting.
Example 1RM Calculation
You bench press 185 lbs for 6 reps. Using Epley: 1RM = 185 × (1 + 6/30) = 185 × 1.20 = 222 lbs. Brzycki: 185 × 36 / (37 – 6) = 185 × 36 / 31 = 215 lbs. Lombardi: 185 × 6^0.10 ≈ 222 lbs. The average is around 220 lbs. The calculator shows these figures and a loading chart so you can program sets at 80% (176 lbs), 85% (187 lbs), etc.
How to Improve Your One Rep Max
To increase your 1RM, focus on progressive overload: gradually add weight or reps over time. Incorporate heavy singles (90%+), triples, and fives into your program. Ensure adequate recovery, nutrition, and sleep. Use this calculator to periodically re‑test your estimated 1RM using a sub‑maximal set, and watch the numbers climb.
Factors That Influence 1RM Estimation
- 🏋️ Weight lifted
- 🔄 Number of reps
- 📏 Exercise performed (upper vs lower body)
- 📅 Fatigue level
- 🧬 Muscle fiber composition
- ⚡ Bar speed and technique
- 📈 Rest periods between sets
- 🏥 Injury history
Detailed Training Scenario
Scenario: Deadlift 315 lbs for 4 reps. Estimates:
- ✅ Epley: 315 × (1 + 4/30) = 357 lbs
- ✅ Brzycki: 315 × 36 / (37‑4) = 344 lbs
- ✅ Lombardi: 315 × 4^0.10 = 356 lbs
- ✅ Average estimated 1RM ≈ 352 lbs
- ✅ 80% of estimated 1RM for working sets: ~282 lbs
Who Can Use This One Rep Max Calculator?
- 🏋️ Powerlifters & strength athletes – program heavy singles and peaking cycles accurately
- 💪 Bodybuilders – set loads for hypertrophy rep ranges based on a percentage of max
- 📋 Coaches & trainers – quickly estimate client 1RM without risk
- 🎓 Fitness beginners – learn your starting strength levels safely
- 📱 Anyone tracking strength gains – measure progress objectively
Key Strength Training Terms
- One Rep Max (1RM)
- The maximum amount of weight you can lift for exactly one repetition with proper form.
- Repetition (Rep)
- One complete motion of an exercise, such as lifting a weight and returning it to the starting position.
- Estimated 1RM
- A predicted maximum lift calculated from a sub‑maximal set, using a formula.
- Percentage‑Based Training
- A programming method where you lift a certain percentage of your 1RM for prescribed reps and sets.
Tips for Accurate 1RM Estimation
- Use a rep range between 1 and 10; formulas lose accuracy above 12‑15 reps.
- Perform the set to genuine muscular failure (or one rep shy) for the most reliable input.
- Test each lift separately — your 1RM will differ for bench, squat, deadlift, etc.
- Re‑test every 4‑6 weeks to update your training loads.
- If you’re new to lifting, prioritize form before chasing max numbers.
Advantages of This 1RM Calculator
- ✅ 100% free – no sign‑up, no ads
- ✅ Instant estimates from five different formulas
- ✅ Generates a full percentage loading table
- ✅ Works in pounds and kilograms
- ✅ Works on any device
- ✅ Private – your lift data never leaves your device
Limitations of 1RM Estimations
All formulas are based on averages and may not perfectly reflect your individual neuromuscular efficiency or technique. The estimates are most reliable for compound lifts and less so for isolation or machine exercises. Always use common sense — an estimated 1RM is a tool, not a guarantee of what you can lift. For competition preparation, a true test under meet conditions is recommended.
Accuracy of Results
The formulas are well‑established in exercise science and generally fall within 5–10% of a true 1RM for most individuals, especially when using ≤10 reps. The average of multiple formulas often yields the closest estimate.
Security and Privacy
All calculations are performed locally in your browser. No weight or rep data is ever transmitted, stored, or shared. You can use the tool offline after the page loads.
Mobile‑Friendly Design
The one rep max calculator is fully responsive. Use it on your smartphone at the gym, on your tablet, or on your desktop — all inputs, charts, and tables adapt seamlessly to any screen size.
Frequently Asked Questions
How accurate is the estimated 1RM?
It’s usually within 5–10% of a true max when using 1‑10 reps. The average of multiple formulas provides a robust estimate, but it’s not a substitute for a true max attempt under controlled conditions.
Can I use this for any exercise?
Yes, but it works best for compound, barbell‑based lifts like squat, bench press, deadlift, and overhead press. It can also be used for dumbbell and machine exercises.
Why are there different formulas?
Each formula was derived from different studies and populations. Epley is the most common, Brzycki is slightly more conservative, and Lombardi is exponential. Comparing them gives a realistic range.
What does the percentage table show?
It displays the weight corresponding to various percentages (50–95%) of your estimated 1RM. Use these numbers for warm‑up sets, working sets, and accessory work.
How often should I test my 1RM?
Every 4–6 weeks is common in periodized programs. You can simply perform a sub‑maximal set to near failure and enter the numbers into the calculator to track changes.
Is my personal data safe?
Absolutely. All calculations are local. No information is ever sent to a server or stored.
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Conclusion: Train Smarter, Get Stronger
Your 1RM is the foundation of serious strength training. This calculator gives you a reliable estimate without the grind and risk of a true max attempt. Use it to set your loads, program your cycles, and watch your numbers climb — all for free and in total privacy.
Ready to Find Your One Rep Max?
Enter your weight and reps now – free, private, and instant.