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One Rep Max

General

One-Repetition Maximum (1RM)

The maximum weight you can lift for a single repetition of an exercise with proper form — the standard benchmark for measuring absolute strength used to prescribe training loads.

Definition

One Rep Max (1RM) is the maximum weight a person can lift for exactly one complete repetition of a given exercise with proper form. It is the gold standard measure of absolute strength for resistance exercises, particularly the barbell squat, bench press, deadlift, and overhead press.

1RM serves as the basis for percentage-based training: prescribing workout weights as a percentage of your maximum, ensuring you train at the right intensity for your goal (endurance, hypertrophy, strength, or power). A programme that says "Squat 5×5 at 80% 1RM" is meaningless without knowing what your 1RM is.

Because directly testing 1RM carries injury risk (especially for beginners), submaximal estimation formulas are commonly used, you perform a set with a challenging but not maximal weight for 2–10 reps, then estimate your 1RM using a formula.

Formula

Epley Formula (most common):

1RM = Weight × (1 + Reps / 30)

Brzycki Formula:

1RM = Weight / (1.0278 − 0.0278 × Reps)

Training Load at % of 1RM:

Working Weight = Estimated 1RM × (Target % / 100)

Both formulas work best for 1–6 rep sets. Accuracy decreases for higher rep sets because muscular endurance becomes a factor.

Worked Example

You bench press 80kg for 5 reps, leaving 1–2 reps in reserve (not complete failure):

Epley: 1RM = 80 × (1 + 5/30) = 80 × 1.167 = 93.3 kg (round to 92.5 kg)

Brzycki: 1RM = 80 / (1.0278 − 0.0278 × 5) = 80 / 0.889 = 90 kg

Using ~90–92kg as your estimated 1RM, training zones would be:

  • 60% (54–55 kg), muscular endurance, 15+ reps
  • 75% (67–69 kg), hypertrophy, 8–12 reps
  • 85% (76–78 kg), strength, 3–5 reps
  • 90–95% (81–87 kg), near-max strength, 1–3 reps

Use the one rep max calculator to instantly estimate 1RM and generate your full training load table.

Key Things to Know

  • 1RM is exercise-specific: Your 1RM for bench press tells you nothing about your 1RM for overhead press. Each exercise has its own 1RM, always test or estimate per-lift.
  • Reps-in-reserve (RIR) matters: Submaximal estimates are most accurate when you stop 1–2 reps before failure. If you could have done 3 more reps, the formula will underestimate your 1RM.
  • Beginners should estimate, not test directly: Without established lifting patterns and neural efficiency, a direct 1RM test is both inaccurate (form breaks down) and risky. Estimate from 3–8 rep sets.
  • Fatigue affects same-session estimates: If you are testing 1RM after a workout, your estimates will be lower. For accurate baseline testing, test fresh, on a day without prior training.
  • TDEE and training load: Heavier training programmes (higher % 1RM, lower reps) burn fewer total calories than high-rep moderate-weight work, despite feeling harder. Factor this into calorie planning when tracking with a TDEE calculator.

Related Calculators

One Rep Max Calculator →Estimate your one rep max (1RM) from any sub-maximal lift using Epley and Brzycki formulas, with training percentages at 90%, 80%, and 70% shown.

Related Terms

TDEETotal Daily Energy ExpenditureBMRBasal Metabolic RateTarget Heart RateExercise Intensity Heart Rate Zone

Frequently Asked Questions

Is it safe to test my actual 1RM?
Testing actual 1RM is safe for experienced lifters who have proper form and an experienced spotter. For beginners or intermediate lifters, using a rep-max formula (estimating 1RM from a set of 3–10 reps) is safer and produces accurate enough results for programming purposes. Direct 1RM testing carries injury risk from maximal loading and is generally reserved for competitive powerlifters.
Which 1RM formula is most accurate?
Most formulas are accurate within 5% for sets of 1–10 reps. Accuracy drops significantly above 10 reps because fatigue becomes a bigger factor than pure strength. The Epley formula (Weight × (1 + Reps/30)) and Brzycki formula (Weight / (1.0278 − 0.0278 × Reps)) are the most widely used and perform comparably for 1–6 rep sets. For practical training purposes, any formula gives a usable estimate.
What percentage of 1RM should I train at for muscle growth?
For hypertrophy (muscle growth), most research supports training in the 60–80% of 1RM range for sets of 6–15 repetitions. The 70–80% range (8–12 reps) is the classic bodybuilding prescription. However, research by Schoenfeld and others has shown that training to failure at lower loads (40–60% 1RM for 15–30 reps) can produce similar hypertrophy, the key variable is proximity to muscular failure, not the exact load.
How often should I test or update my 1RM estimate?
If you are training progressively, your 1RM changes regularly, especially for beginners (who can see strength increases every week). Re-estimate every 4–8 weeks by performing a challenging set (e.g., 3–5 reps near your max) and applying a formula. For a competition lifter, test 1RM in the final weeks of a peaking cycle. Daily 1RM fluctuations (due to sleep, stress, nutrition) can be 5–10%, so avoid making major conclusions from a single test.
How does 1RM relate to a strength training programme?
Most strength and powerlifting programmes prescribe loads as percentages of 1RM. A beginner might squat at 70% of 1RM for 3 sets of 8 reps. An advanced powerlifter might use 90% for singles in competition prep. Knowing your 1RM makes programme prescription precise, ensures progressive overload is measurable, and helps you choose weights that produce the right training stimulus for your goal.