What is the best formula to calculate one-rep max?

For low rep ranges (2–6 reps), the Brzycki formula (Weight × 36 / (37 − Reps)) tends to be most accurate. For moderate ranges (5–10 reps), the Epley formula (Weight × (1 + Reps/30)) is slightly better. Both are accurate within 5–10% for most lifters. Use reps in the 3–8 range for most accurate estimates.

How accurate are 1RM prediction formulas?

For 2–5 rep test sets, predictions are typically within 5% of true 1RM. For 6–10 reps, expect 5–10% error. Beyond 10 reps, accuracy drops significantly — a high-endurance athlete might perform 20 reps at 60% 1RM, while a pure strength athlete might only do 12 at the same percentage, causing formulas to diverge from actual 1RM.

How do I use 1RM for training intensity?

Prescribe training weight as a percentage of 1RM: 80–90% for strength (3–5 reps), 70–80% for hypertrophy (6–12 reps). If your bench 1RM is 200 lbs, a hypertrophy session at 75% = 150 lbs for 8–12 reps per set. Recalculate every 4–8 weeks as strength improves.

Is it safe to test your actual one-rep max?

Direct 1RM testing carries injury risk, particularly for beginners. Proper warm-up, technique, and ideally a spotter are required. For most recreational lifters, predictive formulas from a challenging submaximal set (3–5 rep set) are safer and practical. Reserve true 1RM testing for competitive contexts or when training specifically for maximal strength.

How One-Rep Max Is Calculated: Formulas, Accuracy, and Applications

Calculate your 1RM from submaximal lifts using Epley, Brzycki, and Lander formulas. Understand which formula is most accurate, and how to use 1RM percentages for training intensity.

Related Calculators

One Rep Max Calculator
Estimate your one-rep max (1RM) from a submaximal set, using the Epley formula.
Running Pace Calculator
Calculate your running pace per mile.
Running Record Calculator
Calculate reading accuracy, error rate, and self-correction rate from a running record.
Heart Rate Zone Calculator
Estimate training heart-rate zones from age and resting heart rate using the Karvonen heart-rate-reserve method.
Target Heart Rate Calculator
Calculate your target heart rate training zone from your age.
Therapy Productivity Calculator
Calculate your therapy productivity percentage — billable minutes over paid minutes.

What Is One-Rep Max?

One-rep max (1RM) is the maximum weight you can lift for a single repetition with proper form. It's the standard measure of maximal strength in powerlifting, weightlifting, and strength training programs.

Testing 1RM directly involves attempting maximum loads — which carries injury risk. Predictive formulas estimate 1RM from submaximal lifts (lighter weight for more reps).

The Most Common 1RM Formulas

Epley Formula (1985) — Most widely used: 1RM = Weight × (1 + Reps/30)

Brzycki Formula (1993) — Accurate for low rep ranges: 1RM = Weight × 36 / (37 − Reps)

Lander Formula — Alternative regression: 1RM = (100 × Weight) / (101.3 − 2.67123 × Reps)

Mayhew et al. Formula: 1RM = 100 × Weight / (52.2 + (41.9 × e^(−0.055 × Reps)))

Comparison of Formula Results

For 185 lbs for 6 reps:

Formula	Predicted 1RM
Epley	185 × (1 + 6/30) = 185 × 1.20 = 222 lbs
Brzycki	185 × 36 / (37−6) = 185 × 36/31 = 214.8 lbs
Lander	100 × 185 / (101.3 − 16.03) = 217 lbs

Results cluster around 215–222 lbs depending on formula.

Accuracy by Rep Range

Best accuracy: 2–5 reps (within 5% of true 1RM) Good accuracy: 6–10 reps (within 5–10%) Reduced accuracy: 11–15 reps (within 10–15%) Poor accuracy: 15+ reps (15%+ error common)

Use submaximal sets in the 3–8 rep range for best predictive accuracy.

Training Percentages from 1RM

Once 1RM is known, training intensity is prescribed as percentages:

% of 1RM	Reps in Set	Training Goal
90–100%	1–3	Maximal strength (powerlifting)
80–90%	3–5	Strength development
70–80%	6–12	Hypertrophy (muscle building)
60–70%	10–15	Muscular endurance
50–60%	15–20+	Endurance, warm-up, rehabilitation

Practical application: If your squat 1RM is 300 lbs, a hypertrophy set at 75% would be 225 lbs for 8–12 reps.

Worked Example: Planning a Training Block

Athlete 1RM data: Bench Press 225 lbs, Squat 315 lbs, Deadlift 405 lbs

8-week strength block (80–90% 1RM, 4 sets × 3–5 reps): - Bench: 225 × 0.85 = 191 lbs target working weight - Squat: 315 × 0.85 = 268 lbs - Deadlift: 405 × 0.85 = 344 lbs

Progression: Increase by 5 lbs/week for upper body, 10 lbs/week for lower body over 4–6 weeks, then retest 1RM.

Limitations of 1RM Predictions

Individual fiber type composition affects accuracy (slow-twitch dominant athletes may perform more reps at 80% 1RM than fast-twitch dominant athletes)
Exercise technique affects prediction (experienced lifters are closer to formula predictions)
Fatigue state at time of submaximal test affects results
Different exercises have different prediction accuracy (bench press formulas are more validated than isolation exercises)

Related Guides

Frequently Asked Questions

What is the best formula to calculate one-rep max?: For low rep ranges (2–6 reps), the Brzycki formula (Weight × 36 / (37 − Reps)) tends to be most accurate. For moderate ranges (5–10 reps), the Epley formula (Weight × (1 + Reps/30)) is slightly better. Both are accurate within 5–10% for most lifters. Use reps in the 3–8 range for most accurate estimates.
How accurate are 1RM prediction formulas?: For 2–5 rep test sets, predictions are typically within 5% of true 1RM. For 6–10 reps, expect 5–10% error. Beyond 10 reps, accuracy drops significantly — a high-endurance athlete might perform 20 reps at 60% 1RM, while a pure strength athlete might only do 12 at the same percentage, causing formulas to diverge from actual 1RM.
How do I use 1RM for training intensity?: Prescribe training weight as a percentage of 1RM: 80–90% for strength (3–5 reps), 70–80% for hypertrophy (6–12 reps). If your bench 1RM is 200 lbs, a hypertrophy session at 75% = 150 lbs for 8–12 reps per set. Recalculate every 4–8 weeks as strength improves.
Is it safe to test your actual one-rep max?: Direct 1RM testing carries injury risk, particularly for beginners. Proper warm-up, technique, and ideally a spotter are required. For most recreational lifters, predictive formulas from a challenging submaximal set (3–5 rep set) are safer and practical. Reserve true 1RM testing for competitive contexts or when training specifically for maximal strength.

Last updated 7/28/2026