One Rep Max Calculator
Calculate your 1RM for any lift using 7 formulas compared side by side — not just Epley. Get a full training percentage table with colour-coded zones, powerlifting total with Wilks score, and your strength level by bodyweight.
One Rep Max Calculator Tool
| Formula | Estimated 1RM | Best rep range | Relative |
|---|
| % of 1RM | Weight | Typical reps | Training zone | Goal |
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The most complete free 1RM calculator — 7 formulas, Wilks score and strength standards
Most free one rep max calculators use one formula only — usually Epley — and show nothing else. This tool shows all seven major validated formulas side by side, recommends the best one for your rep range, and adds features not found anywhere else for free.
How to calculate your one rep max
How this 1RM calculator compares
| Feature | LazyTools ✦ | Omnicalculator | Calculator.net | Strength Journeys |
|---|---|---|---|---|
| Number of 1RM formulas shown | ✔ 7 formulas | 4 formulas | 3 formulas | 7 formulas |
| Formula recommendation by rep range | ✔ Yes | ✘ No | ✘ No | ✔ Yes |
| Training % table (colour-coded zones) | ✔ 50–100% with zones | ✔ Partial | ✔ Basic | ✘ No |
| Powerlifting total (S+B+D) | ✔ Yes | ✘ No | ✘ No | ✘ No |
| Wilks score calculator | ✔ Yes | ✔ Separate page | ✘ No | ✘ No |
| Strength standards gauge by bodyweight | ✔ 5 levels | ✘ No | ✘ No | ✘ No |
| Kg / lbs toggle | ✔ Yes | ✔ Yes | ✔ Yes | ✔ Yes |
| Lift selector (bench, squat, DL, OHP) | ✔ 5 lifts | ✔ Some | ✘ Generic | ✘ Generic |
| No ads blocking results | ✔ Clean layout | Ads | Heavy ads | ✔ Clean |
| All features on one page, no navigation needed | ✔ Yes | Multiple pages | Multiple pages | Multiple pages |
The 7 one rep max formulas — equations and accuracy
| Formula | Equation | Best rep range | Notes |
|---|---|---|---|
| Epley | w × (1 + r/30) | 6–10 reps | Most widely cited; used by NSCA. Slightly overestimates at high reps. |
| Brzycki | w × 36 / (37 − r) | 1–10 reps | Second most popular. More conservative than Epley above 10 reps. |
| Lombardi | w × r^0.10 | 1–5 reps | Exponential model. Slightly lower estimates than Epley; good for low reps. |
| Mayhew | 100 × w / (52.2 + 41.9 × e^(−0.055 × r)) | 6–15 reps | Exponential decay. Originally derived from bench press data. |
| O'Conner | w × (1 + r/40) | 1–20 reps | Simplest formula — 2.5% per rep. Conservative; easy to calculate mentally. |
| Wathen | 100 × w / (48.8 + 53.8 × e^(−0.075 × r)) | 1–6 reps | Exponential model from trained lifters. Agrees with Epley at low reps. |
| Lander | (100 × w) / (101.3 − 2.67123 × r) | 1–10 reps | Linear model; results between Brzycki and Epley. Widely used academically. |
One Rep Max Calculator — Everything You Need to Know About 1RM, Training Percentages and Strength Programming
Your one rep max (1RM) is the maximum weight you can lift for a single complete repetition with proper form in a given exercise. It is the gold standard measure of absolute strength and the foundation of almost all structured strength training programming. Knowing your 1RM allows you to calculate precise training loads as percentages, track strength progress over time, set meaningful targets, and compare your strength to standards for your bodyweight and experience level. Whether you train for powerlifting, general fitness, bodybuilding or sport performance, the 1RM and the percentage-based training zones derived from it are the most widely used framework for designing effective, progressive resistance programmes.
Why test or calculate 1RM rather than lifting to failure?
Directly testing a true 1RM — progressively adding weight until only one rep can be completed — is accurate but carries risks. Without an experienced spotter, proper technique often breaks down at maximal loads, increasing injury risk. True max testing is also neurologically and physically fatiguing, requiring significant recovery time. Submaximal prediction formulas solve this by estimating 1RM from a safer, controlled set at a moderate rep range. Performing a challenging set of 3–6 reps at a weight you are familiar with provides a reliable 1RM estimate while keeping the session manageable and the risk low. Most experienced strength coaches recommend estimating 1RM from submaximal sets during normal training and testing a true 1RM only two to four times per year, typically before competitive events or major programming cycles.
The 7 major 1RM prediction formulas explained
Seven validated formulas are widely used for 1RM prediction, each with slightly different mathematical approaches and accuracy profiles. Epley (1985) is the most commonly cited and is used by the NSCA; it works best for 6–10 rep sets and tends to slightly overestimate at higher rep counts. Brzycki (1993) is the second most popular and is more conservative than Epley above 10 reps, making it arguably more realistic for higher-rep sets while closely matching Epley for 1–5 rep sets. Lombardi uses an exponential model and produces slightly lower estimates, making it well-suited for very low rep sets (1–5). Mayhew uses an exponential decay function originally derived from bench press research; it produces moderate estimates between Epley and Lombardi and works well across a broad rep range. O'Conner is the simplest formula — adding 2.5% of the working weight per rep — making it easy to calculate mentally but producing the most conservative estimates overall. Wathen was developed from data across multiple exercises with trained lifters and tends to agree closely with Epley for low-rep sets while being more conservative at higher reps. Lander uses a linear model and produces results that sit between Brzycki and Epley, making it a popular academic choice. No single formula universally outperforms the others; using the average of multiple formulas reduces any individual formula's bias and produces a more robust estimate.
Training percentage zones — how to use your 1RM in programming
Once you have your estimated 1RM, you can express all training loads as percentages of that maximum, making programming systematic and measurable. The major training zones are: Power and explosiveness (50–65% 1RM) — light loads moved as fast as possible, developing rate of force development; Strength endurance (65–75% 1RM) — moderate loads for 8–15 reps, building muscular endurance and metabolic conditioning; Hypertrophy (75–85% 1RM) — the primary zone for muscle growth at 6–12 reps, balancing mechanical tension with metabolic stress; Maximal strength (85–95% 1RM) — heavy loads for 1–5 reps, building neural adaptations and raw strength; Peaking (95–100% 1RM) — near-maximal loads for singles and doubles, used in competition preparation. Most evidence-based programming cycles rotate through these zones periodically, a practice known as periodisation.
What is the Wilks score and how is it calculated?
The Wilks score was developed by Robert Wilks of Powerlifting Australia and is used in powerlifting competitions to compare strength across different bodyweights and sexes. The formula multiplies total weight lifted by a coefficient derived from the lifter's bodyweight using a polynomial equation. Because heavier individuals tend to lift more in absolute terms, the Wilks coefficient decreases as bodyweight increases, normalising totals so that a 60 kg lifter and a 120 kg lifter can be compared fairly. A Wilks score above 300 is generally considered competitive at a recreational level, above 400 is strong at a national amateur level, and scores above 500 are seen at the top of elite international competition. The Wilks formula was updated in 2020 — the newer IPF GL (Good Lift) coefficient has since been adopted by the International Powerlifting Federation for official competition, but the Wilks score remains widely used and understood.
Strength standards by bodyweight — what is a good 1RM?
Strength standards vary by exercise, sex and experience level. Bench press bodyweight multiplier standards for male lifters are approximately: Beginner = 0.5× bodyweight; Novice = 0.75×; Intermediate = 1.0×; Advanced = 1.25×; Elite = 1.5× or above. Back squat standards follow as Beginner = 0.75×; Novice = 1.0×; Intermediate = 1.25×; Advanced = 1.5×; Elite = 1.75× or more. Deadlift standards are: Beginner = 1.0×; Novice = 1.25×; Intermediate = 1.5×; Advanced = 1.75×; Elite = 2.0×. Female standards are approximately 20–30% lower in absolute bodyweight multiples across all lifts. These are broad benchmarks — individual variation, training age, body proportions and genetics all significantly affect what is achievable.
How often should you recalculate your 1RM?
Most strength coaches recommend recalculating your estimated 1RM every 4–6 weeks, or whenever you feel significantly stronger than your last calculation. This keeps training loads calibrated to your current strength level as you progress. During a dedicated strength block, your 1RM might increase by 2–5% every 4–6 weeks in the early to intermediate stages, and more slowly — 1–2% — as you become more advanced. After a deload week or a period of reduced training, your 1RM may temporarily decrease and then recover quickly when full training resumes. Tracking your calculated 1RM over time — even if you never test a true maximum — gives a clear record of long-term strength development.
Periodisation — cycling through training zones
Periodisation is the practice of systematically varying training intensity and volume over time to maximise long-term strength gain while managing fatigue. A classic linear periodisation scheme begins a training block with higher-volume, lower-intensity work (70–80% 1RM for 8–12 reps) and progresses to lower-volume, higher-intensity work (90–97% 1RM for 1–3 reps) as the competition or test date approaches. Undulating periodisation varies the training zone within a single week — for example, heavy strength work on Monday, hypertrophy work on Wednesday and power work on Friday — all based on percentages of the same 1RM. Knowing your 1RM is the anchor for both approaches. Recalculate at the start of each training block and update your absolute weights accordingly, since a weight that was 75% of your 1RM three months ago may now represent only 70% as you have grown stronger.