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🏋️ 1RM 🆓 Free 7 Formulas

🏋️ One-Rep Max Calculator

Enter any weight and rep count to instantly estimate your 1RM using 7 validated formulas - Epley, Brzycki, Lander, Lombardi, Mayhew, O'Conner, and Wathan - with an averaged result for best accuracy. The training percentage chart shows your working weights for strength, hypertrophy, and power goals from 50% to 100% of 1RM.

🏋️ 1RM Calculator

Weight Unit

️ Never attempt a true 1RM without an experienced spotter. Estimated 1RMs are most accurate for reps in the 2–6 range. Accuracy decreases above 10 reps.

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kg - Estimated 1RM (Epley Formula)

Training Percentage Chart

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Reps % of 1RM Weight Zone Goal
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🏆 Strength Standards

Compare your estimated 1RM to population strength standards (bodyweight multiples). Select your exercise above.

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1RM Formulas Explained

Epley Formula (Most Common)

1RM = w × (1 + r/30) w = weight lifted r = reps performed Example: 100 kg × 5 reps 1RM = 100 × (1 + 5/30) = 100 × 1.167 = 116.7 kg Best for: General use, most commonly referenced. Tends to slightly overestimate at high reps.

Brzycki Formula

1RM = w × (36 / (37 - r)) Example: 100 kg × 5 reps 1RM = 100 × (36 / (37 - 5)) = 100 × (36 / 32) = 112.5 kg Best for: Lower rep ranges (1–10). Slightly more conservative than Epley.

Lander Formula

1RM = (100 × w) / (101.3 - 2.67123 × r) Example: 100 kg × 5 reps 1RM = 10000 / (101.3 - 13.356) = 10000 / 87.944 = 113.7 kg

Other Formulas

Lombardi: 1RM = w × r^0.10 Mayhew: 1RM = (100 × w) / (52.2 + 41.9 × e^(-0.055 × r)) O'Conner: 1RM = w × (1 + 0.025 × r) Wathan: 1RM = (100 × w) / (48.8 + 53.8 × e^(-0.075 × r)) Best practice: Use the AVERAGE of all formulas for the most reliable estimate, especially when reps are in the 3-8 range.

Training Zones by % of 1RM

95–100%: Max Strength (1–2 reps) - true 1RM zone 90–95%: Strength (2–3 reps) 85–90%: Strength/Power (3–5 reps) 80–85%: Strength/Hypertrophy (5–6 reps) 70–80%: Hypertrophy (8–12 reps) MUSCLE GAIN 60–70%: Hypertrophy/Endurance (12–15 reps) 50–60%: Muscular Endurance (15–20 reps) Below 50%: Warm-up / technique work

Frequently Asked Questions

A one-rep max (1RM) is the maximum weight you can lift for exactly one repetition with proper form. It is the gold standard measure of absolute strength. Rather than testing it directly (injury risk and CNS fatigue), you lift a submaximal weight for multiple reps and use a validated formula to estimate. The 1RM is useful for: setting precise training loads by percentage, tracking strength progress over time, comparing to bodyweight-relative strength standards, and following structured percentage-based programs.
Epley and Brzycki are the most commonly used and validated. At 2–6 reps: all formulas are within 3–6% of each other and reasonably accurate. At 7–10 reps: accuracy decreases and results diverge. At 11–15 reps: error can reach 15–20% depending on your muscle fiber type. The best single approach is averaging all formulas - which this calculator does automatically. For best accuracy regardless of formula, use 3–5 rep sets at approximately 85% of perceived maximum.
Accuracy decreases as rep count increases because individual strength-to-endurance ratios vary significantly. At 3–5 reps: typical error 3–5%. At 8–10 reps: error 8–12%. At 12–15 reps: error can exceed 15%. Strength-dominant athletes (fast-twitch fiber heavy) will overpredict at high reps because they fatigue faster than the formula assumes. Endurance athletes may underpredict. This is why 3–6 rep sets are recommended for 1RM estimation - they give the most formula-independent accurate result.
Strength (1–5 reps): 80–95% of 1RM. Hypertrophy/mass (6–12 reps): 65–80%. Power and speed work: 50–70% with maximal intent. Endurance/conditioning: 50–65% at 15+ reps. For periodisation: start a training block at lower percentages (70–75%) and progress to higher percentages (85–90%) over 4–8 weeks. Recalculate 1RM every 4–6 weeks for beginners (improving rapidly) and every 8–12 weeks for intermediate and advanced lifters.
For beginners (under 12 months consistent training): No - injury risk is high and submaximal estimation is sufficient. For intermediate/advanced: Testing occasionally (every 3–6 months) provides a verified benchmark. Proper protocol: full warm-up, then progressive attempts at 60%, 70%, 80%, 85%, 90%, 95%, 100%. Rest 3–5 minutes between attempts. Have a spotter for barbell movements. Only attempt if sleep, nutrition, and recovery are adequate. A competition or peaking phase is the ideal time for true 1RM testing.
General bodyweight-relative standards for adult males (intermediate level): Bench press: 1× bodyweight. Squat: 1.5× bodyweight. Deadlift: 2× bodyweight. For females: approximately 60–75% of the male standard relative to bodyweight. Advanced standards: Bench 1.5× BW, Squat 2× BW, Deadlift 2.5× BW. Elite powerlifters regularly bench 2× BW, squat 3× BW, deadlift 3.5× BW. Use these as general benchmarks - training age, natural leverage differences, and genetics all affect what is achievable.
Progressive overload means consistently increasing training stress to drive ongoing adaptation. The most common form is adding weight over time - measured as an increasing 1RM. When your 1RM increases, recalculate your training percentages: if 1RM was 100 kg and you're using 80% (= 80 kg), and 1RM grows to 110 kg, your 80% weight becomes 88 kg. This maintains the same relative training stimulus. Without recalculating from a current 1RM, you risk training at percentages that are too easy (no adaptation) or too heavy (excessive fatigue and injury risk).
Rate of improvement depends heavily on training age and proximity to genetic potential. Beginners (0–12 months): 2.5–5 kg/week on squat/deadlift, 1–2.5 kg/week on bench (fastest gains, primarily neural). Intermediate (1–3 years): 2.5–5 kg/month. Advanced (3+ years): 2.5–5 kg over 3–6 months. Strength gain rate slows as you approach your ceiling. Nutrition is critical - adequate protein (1.6–2.2g/kg body weight) and sufficient total calories support strength gains. Sleep quality directly impacts both recovery and CNS performance under heavy loads.

🏋️ Training Zones Quick Ref

95–100%Max strength
85–95%Strength
75–85%Strength/Hypertrophy
65–75%Hypertrophy
55–65%Endurance
Best formula range2–6 reps

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One Rep Max Calculator - 1RM Estimation, Training Percentages & Strength Standards

Your one rep max is the foundation of percentage-based strength programming. Without it, you're guessing at working weights. With it, you can precisely calculate exactly how heavy to lift for every set in every session - whether you're training for strength, size, or power. This calculator estimates your 1RM from any submaximal effort and then maps out your entire training range from that number.

Quick example: You bench press 80 kg for 5 reps. Epley formula: 80 × (1 + 5÷30) = 80 × 1.167 = 93.3 kg estimated 1RM. Training percentages: 80% = 74.7 kg (hypertrophy working weight). 85% = 79.4 kg (strength). 90% = 84 kg (near-max singles). The calculator computes all 7 formulas and averages them.

The 7 1RM Formulas - How They Differ

Seven validated formulas are used in this calculator. They were developed from different research populations and use slightly different mathematical relationships between reps, weight, and estimated 1RM:

Most Widely Used

  • Epley (1985): 1RM = w × (1 + r÷30). Most commonly referenced. Good for 2–10 reps.
  • Brzycki (1993): 1RM = w × 36÷(37−r). Strong accuracy at 2–10 reps. Gives slightly lower estimates than Epley.
  • Lander (1985): 1RM = 100×w÷(101.3 − 2.67123×r). Good balance across rep ranges.
  • Lombardi (1989): 1RM = w × r^0.10. Unique power-based formula.

Specialised Formulas

  • Mayhew et al. (1992): 1RM = 100×w÷(52.2 + 41.9×e^(−0.055×r)). Developed from bench press research.
  • O'Conner et al. (1989): 1RM = w×(1 + 0.025×r). Conservative formula giving lower estimates.
  • Wathan (1994): 1RM = 100×w÷(48.8 + 53.8×e^(−0.075×r)). Similar to Mayhew.
  • The averaged result across all 7 is the most reliable single estimate.

Training Zones by Goal - How to Use Your 1RM

Once you know your 1RM, use these percentage ranges to set working weights for every training goal:

  • Strength (1–5 reps at 80–95% 1RM): Develops maximal force production. Neural adaptations dominate. High CNS demand - needs adequate rest (3–5 minutes between sets). Core of powerlifting programming (5/3/1, Wendler, Texas Method).
  • Hypertrophy (6–12 reps at 65–80% 1RM): Maximises muscle growth through metabolic stress and mechanical tension. The "bodybuilding range." Most evidence supports this zone for mass gain. Shorter rest (1–2 minutes) increases metabolic stimulus.
  • Power/Olympic lifting (1–3 reps at 50–70% 1RM with maximal speed): Lower load, maximum bar speed. Develops explosive force. Cleans, snatches, jump squats.
  • Muscular endurance (15+ reps at 50–65% 1RM): Builds local muscular endurance and cardiovascular capacity. High rep ranges. Sports conditioning and circuit training.

Why Not Just Test Your 1RM Directly?

Direct 1RM testing is used by competitive powerlifters and Olympic weightlifters, but for most gym-goers the risks often outweigh the benefits:

  • Injury risk: Maximum attempts demand perfect form at maximum load - any technical breakdown under a true 1RM can cause significant injury. This is particularly true for the spine and shoulders.
  • CNS fatigue: True maximal efforts are extremely taxing on the central nervous system. A single 1RM test disrupts training for 2–3 days. Submaximal estimation avoids this cost.
  • Accuracy issues: A "true" 1RM on any given day is influenced by sleep, nutrition, warm-up quality, and psychological state. Multiple submaximal estimates averaged over weeks are often more reliable as a training baseline than a single maximum attempt.

When to test directly: when you want a verified competitive number, when you've been training systematically for at least 6 months, and with a spotter present and a thorough warm-up protocol. For programming purposes, an estimated 1RM from a clean 3–5 rep set is entirely sufficient.

How this calculator works, and where the numbers come from

The One Rep Max (1RM) applies the standard formula for this calculation to the values you enter and updates the result as you type. The calculation itself happens in your browser, and the page explains the method so you can check any result by hand.

Please note: This tool gives general estimates based on published population formulas. It is not medical advice and does not replace assessment by a doctor, dietitian or other qualified professional.

Sources and further reading

Last reviewed: by the CalcQube Editorial Team. See our editorial policy for how we build and check calculators, or report an error.