One Rep Max (1RM) Calculator

Calculate your max strength using 4 validated formulas — instantly build your training percentages

🏋️ Epley · Brzycki · Lombardi · O’Conner 📊 Rep Scheme Table 🏆 Strength Standards
Your Lift Details
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Estimated One Rep Max
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Formula Breakdown
Epley
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Brzycki
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Lombardi
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O’Conner
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Recommended 1RM = average of all four formulas

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Training Percentages & Rep Scheme
% of 1RM Weight (kg) Suggested Reps Training Zone
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What Is a One Rep Max (1RM)?

Your one rep max (1RM) is the maximum amount of weight you can lift for exactly one repetition with proper form. It’s the gold standard of measuring absolute strength in powerlifting, weightlifting, and strength training. Whether you’re training for the Bench Press, Squat, Deadlift, or Overhead Press, knowing your 1RM lets you program your training with scientific precision.

Most lifters don’t test their 1RM directly because it carries injury risk — especially for newer athletes. Instead, you perform a set of submaximal reps (e.g. 5 reps at 80%) and use a validated formula to estimate your true 1RM. That’s exactly what this 1RM calculator does.

Why Does Your 1RM Matter?

Knowing your one rep max unlocks percentage-based programming — the backbone of virtually every proven strength protocol including 5/3/1, Conjugate Method, Texas Method, and GZCLP. By training at specific percentages of your 1RM, you can:

  • Target specific adaptations (strength vs. hypertrophy vs. power)
  • Auto-regulate load based on readiness
  • Track progress objectively over weeks and months
  • Compare yourself to established strength standards
  • Design intelligently periodised training blocks

How to Safely Test Your 1RM

If you want an accurate 1RM, testing it directly is the most precise method. Follow this protocol:

  • Warm up thoroughly: 10 min of general cardio, then progressive warm-up sets — 50% × 8, 65% × 5, 75% × 3, 85% × 1, 90% × 1
  • Rest 3–5 minutes between heavy attempts
  • Attempt your 1RM: Choose a weight you’re confident you can lift once but not twice
  • Limit attempts to 3 max: Fatigue degrades performance and increases injury risk
  • Don’t test on consecutive days: Allow 48–72 hours before testing another lift
  • Have a spotter: Essential for Bench Press; advisable for Squat

The Four 1RM Formulas Explained

This calculator uses four scientifically validated formulas and averages them for the most reliable estimate.

1. Epley Formula (1985)

1RM = Weight × (1 + Reps / 30)

Developed by Boyd Epley at the University of Nebraska. One of the earliest and most widely cited 1RM formulas. Performs well across most rep ranges but can slightly overestimate at higher rep counts.

2. Brzycki Formula (1993)

1RM = Weight × (36 / (37 − Reps))

Developed by Matt Brzycki. Widely used in athletic training programs. Generally considered most accurate for 2–10 rep ranges and tends to give conservative (safer) estimates.

3. Lombardi Formula

1RM = Weight × Reps0.10

A simpler exponential model that works particularly well for lower rep ranges (1–6). Can produce higher estimates for longer rep sets.

4. O’Conner Formula

1RM = Weight × (1 + 0.025 × Reps)

A conservative linear model. Tends to underestimate slightly but is useful as a lower bound, especially for higher rep ranges (8–12).

Training Zone Reference

Once you know your 1RM, here’s how to apply percentages to different training goals:

  • 90–100% 1RM (1–3 reps): Maximal strength, neuromuscular adaptation
  • 80–89% 1RM (3–5 reps): Strength + some hypertrophy (powerbuilding sweet spot)
  • 70–79% 1RM (5–8 reps): Hypertrophy + strength endurance
  • 60–69% 1RM (8–12 reps): Primary hypertrophy range
  • Below 60% (12+ reps): Muscular endurance, technique, warm-ups

Frequently Asked Questions — 1RM Calculator

Is the estimated 1RM accurate? +
Estimated 1RMs are generally accurate within 2–5% when calculated from sets of 3–6 reps. Accuracy decreases as rep count increases. Using 10+ reps can produce estimates 10–15% off from your true 1RM. For the best estimate, use a weight you can lift 3–6 times with excellent form but not 7. Our calculator averages four formulas to minimise individual formula error.
How often should I test my 1RM? +
For most lifters, testing a true 1RM every 8–16 weeks (at the end of a training block) is sufficient. More frequent testing adds unnecessary fatigue and injury risk without meaningful feedback. Instead, re-estimate your 1RM regularly by using this calculator after your heaviest working sets.
What is a good 1RM for Bench Press / Squat / Deadlift? +
Strength standards are relative to your bodyweight. Using Symmetric Strength standards (male): an intermediate male lifter should Bench Press ~1.0× bodyweight, Squat ~1.5× bodyweight, and Deadlift ~1.75× bodyweight. For females, multiply those ratios by roughly 0.75. Enter your bodyweight above to see your personalised standards.
Which 1RM formula is most accurate? +
No single formula is most accurate for every person. Research suggests Brzycki performs best for 2–8 rep ranges, while Epley is generally reliable across broader ranges. O’Conner tends to give conservative estimates. Averaging multiple formulas — as this calculator does — consistently outperforms any single formula, which is why we use all four.
What is progressive overload and how does 1RM relate to it? +
Progressive overload is the gradual increase of training stress over time — the fundamental principle of strength and muscle development. Your 1RM is the reference point. As your 1RM increases, all your training weights (calculated as percentages) automatically scale up. Tracking your 1RM over months is the clearest evidence of progressive overload working.
Can beginners test their 1RM? +
We don’t recommend beginners test their true 1RM. Beginners gain strength very rapidly (often week to week), making 1RM testing redundant — any number you test today will be outdated next week. More importantly, beginners have not yet developed the technical proficiency or neuromuscular coordination to lift maximal loads safely. Use this calculator with your 5-rep weights instead.
Does creatine increase your 1RM? +
Yes — creatine monohydrate is the most extensively researched performance supplement in existence, with hundreds of peer-reviewed studies confirming its effectiveness. It increases phosphocreatine stores in muscle, which directly fuels ATP regeneration during maximal and near-maximal efforts. Meta-analyses consistently show 5–15% improvements in maximal strength with creatine supplementation compared to placebo.
How do I use the rep percentage table for programming? +
The rep scheme table above shows the standard training percentages used in evidence-based programs. For example, in Jim Wendler’s 5/3/1, your “top set” on Week 1 is 85% × 5+, Week 2 is 90% × 3+, and Week 3 is 95% × 1+. Simply read those weights directly from the table. For hypertrophy work, your back-off sets typically sit at 65–75% of 1RM for 8–12 reps.
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