Knowing your one rep max is fundamental to effective strength training. Our free 1RM calculator estimates your maximum single-rep lift using five research-backed formulas — Brzycki, Epley, Lander, Lombardi, and O'Conner. Enter any weight and rep count to get your estimated max plus a complete percentage chart for programming your workouts. No guesswork, no dangerous maximal testing, no sign-up required.
The one rep max (1RM) is the heaviest weight you can lift for one complete repetition with proper form. It is the universal measure of maximal strength and the foundation for percentage-based training programs. Rather than attempting a dangerous all-out single, 1RM calculators use submaximal performance (a weight lifted for multiple reps) to estimate your true max through validated mathematical formulas. The five most established formulas — Brzycki, Epley, Lander, Lombardi, and O'Conner — each use slightly different mathematical models, and comparing results across formulas gives you a reliable estimated range.
Five formula comparison (Brzycki, Epley, Lander, Lombardi, O'Conner). Percentage-based loading chart from 50% to 100% of estimated 1RM. Rep range equivalents for each percentage (how many reps you should get at each weight). Support for pounds and kilograms. Works for any barbell exercise (squat, bench, deadlift, press). Instant calculation with no loading. Mobile-friendly for gym use. Client-side processing — no data shared. No registration required.
You enter the weight you lifted and the number of reps completed (ideally a set taken to or near failure). The calculator applies all five formulas simultaneously: Brzycki uses the relationship weight × 36/(37 − reps), Epley uses weight × (1 + reps/30), and the others apply their own coefficients. Each formula estimates what weight you could lift for exactly one rep. The percentage chart then divides your estimated 1RM into training loads — 95%, 90%, 85%, etc. — with corresponding rep expectations at each percentage.
Strength Program Setup — Setting accurate working weights for programs like 5/3/1, Starting Strength, and Juggernaut Method. Progress Tracking — Monitoring estimated 1RM increases over training cycles. Powerlifting Prep — Planning attempts for competition without overtesting in training. Personal Training — Coaches prescribing individualized loads for clients. Returning From Injury — Establishing a safe baseline without maximal testing. Workout Planning — Determining appropriate warm-up progressions and working set weights. Competition Planning — Selecting opening, second, and third attempts based on training estimates.
Testing a true 1RM is risky, fatiguing, and requires experienced spotters. A calculator gives you a reliable estimate from a safer submaximal set — typically 3–6 reps with a heavy weight. By comparing five formulas, you get a range rather than a single number, which accounts for individual variation. The built-in percentage chart translates your max directly into training loads, saving you from doing the math during workouts. Recalculate periodically to track strength gains objectively.
Strength athletes following percentage-based programs. Powerlifters planning competition attempts. Personal trainers prescribing loads for clients. Recreational lifters wanting to train with appropriate intensity. Anyone returning from a layoff who needs to re-establish working weights. Coaches managing team strength training. Beginners who should not be attempting true maximal lifts. CrossFit athletes calculating prescribed loads.
Choose a major compound lift (squat, bench press, deadlift, overhead press). After a thorough warm-up, perform a set of 3–6 reps with a challenging weight — you should feel like you had 0–1 reps left in reserve. Enter the weight and reps into the calculator. Compare the results across formulas and use the average or the Brzycki/Epley result as your working estimate. Apply a 90% training max for conservative programming. Use the percentage chart to load your working sets.
Use Low Rep Sets — 1–6 reps produce the most accurate estimates; avoid using sets of 10+. Go Near Failure — The set should be a true maximum effort for that rep count (RPE 9–10). Warm Up Properly — Progressive warm-up sets prevent injury and prime your nervous system. Use a Training Max — Program off 85–90% of your estimated 1RM for sustainable progression. Track Per Exercise — Calculate separately for each lift; ratios between lifts vary by individual. Recalculate Regularly — Every 4–6 weeks or after significant rep PRs. Round Practically — Round to the nearest available plate increment (5 lbs or 2.5 kg).
Accuracy decreases above 10 reps as cardiovascular fatigue becomes a factor. Individual variation means your actual 1RM may differ 5–10% from estimates. Formulas assume proper form — if reps are achieved with degraded technique, the estimate may be inflated. 1RM estimates do not account for peaking (the trained ability to express strength in a single rep). Drug-free and enhanced lifters may respond differently. The calculator estimates the weight you could lift, not the weight you should lift — always prioritize form and safety.
A one rep max (1RM) is the maximum weight you can lift for a single repetition with proper form. It is the gold standard for measuring absolute strength in a given exercise. Knowing your 1RM is essential because most strength training programs prescribe loads as percentages of 1RM — for example, 'squat 5×5 at 80% 1RM.' Without knowing your 1RM, you cannot accurately follow percentage-based programs like 5/3/1, Starting Strength, or Juggernaut Method.
Brzycki: 1RM = weight × (36 / (37 − reps)). Most accurate for 1–6 reps. Epley: 1RM = weight × (1 + reps/30). Slightly higher estimates, popular in powerlifting. Lander: 1RM = (100 × weight) / (101.3 − 2.67123 × reps). Good for moderate rep ranges. Lombardi: 1RM = weight × reps^0.1. Conservative estimates. O'Conner: 1RM = weight × (1 + reps/40). Most conservative. For 1–5 reps, all formulas produce similar results. Divergence increases above 8 reps. Most coaches use Brzycki or Epley.
With 1–6 reps, 1RM formulas are accurate within 5% for most trained lifters. At 7–10 reps, accuracy drops to within 10%. Above 10 reps, estimates become unreliable because fatigue, form breakdown, and cardiovascular limitations cloud the relationship between submaximal weight and true max. Individual variation also matters — some people are better at grinding heavy singles while others excel at higher rep sets. Use your estimate as a starting point and adjust based on actual performance.
For most people, a calculator is safer and sufficient. Testing a true 1RM carries injury risk, especially for beginners, and requires: proper warm-up protocol (progressively heavier singles), a competent spotter, and experience with near-maximal loads. Competitive powerlifters and Olympic lifters should periodically test actual 1RMs. Recreational lifters and those following percentage-based programs can use calculated estimates and adjust. Many programs use a 'training max' (90% of estimated 1RM) to account for estimation error.
A training max is typically 85–90% of your estimated 1RM, used as the basis for programming instead of your true max. Programs like 5/3/1 by Jim Wendler explicitly use a training max to ensure you can always complete prescribed reps with good form. Example: If your estimated 1RM squat is 300 lbs, your training max would be 270 lbs (90%). When the program says '5 reps at 85%,' you calculate 85% of 270 (230 lbs), not 85% of 300. This builds in a buffer for bad days and ensures progressive overload.
The percentage chart shows estimated weight for each percentage of your 1RM: 100% = 1 rep (max), 95% ≈ 2 reps, 90% ≈ 3–4 reps, 85% ≈ 5 reps, 80% ≈ 6–8 reps, 75% ≈ 8–10 reps, 70% ≈ 10–12 reps, 65% ≈ 12–15 reps, 60% ≈ 15–20 reps. Strength work typically uses 80–95%, hypertrophy 65–80%, endurance 50–65%. Round weights to the nearest 5 lbs or 2.5 kg for practical loading.
Recalculate every 4–6 weeks during a training cycle, or whenever you hit a significant rep PR. If you are progressing linearly (adding weight each session), you may need to recalculate every 2–3 weeks. After a deload week or training break, test with a moderate weight for 3–5 reps to re-establish your baseline. Avoid recalculating based on a single great day or a bad day — use a performance that feels representative of your current ability.
Absolutely. You will have different 1RMs for every exercise — your squat 1RM will differ from your bench press, deadlift, overhead press, etc. Strength ratios vary between individuals based on limb proportions, training history, and muscle development. Common benchmarks for intermediate male lifters: Deadlift > Squat > Bench Press > Overhead Press, with approximate ratios of 1.25:1:0.75:0.5. Always calculate and track 1RM separately for each major lift.