One Rep Max Calculator
Enter a lifted weight and reps to estimate your 1RM and see your working weights at every percentage — calculated in your browser.
Estimates only. Accuracy decreases above 10 reps. For general guidance; consult a certified coach for programming.
How to use One Rep Max Calculator
The one-rep max (1RM) calculator estimates the maximum weight you could lift for a single repetition of any exercise, based on a submaximal set of weight and reps. Two formulas are computed — Epley and Brzycki — and their average is displayed to give a more robust estimate. A full percentage training table from 50% to 100% of your 1RM shows the working weight for each intensity zone, which is the cornerstone of percentage-based strength programming.
- Select your weight unit (kg or lbs).
- Enter the weight you lifted (e.g. 100 kg).
- Enter the number of repetitions you completed before failure or near-failure (1–36).
- Click Calculate 1RM to see Epley, Brzycki and average estimates.
- Use the percentage table to find your working weights for training sets at any intensity.
Your data never leaves your device — 100% private processing.
Epley vs Brzycki: which formula to use?
The Epley formula (1985) calculates 1RM = weight × (1 + reps ÷ 30) and is among the most widely cited. The Brzycki formula (1993) calculates 1RM = weight ÷ (1.0278 − 0.0278 × reps) and tends to give slightly lower estimates, particularly at higher rep counts. Both formulas are more accurate in the 1–10 rep range; accuracy degrades above 10 reps because the weight–rep relationship is not perfectly linear. Using the average of both reduces formula-specific bias and is generally preferred for programming purposes.
| Formula | Year | Equation | Best range |
|---|---|---|---|
| Epley | 1985 | weight × (1 + reps/30) | 1–10 reps |
| Brzycki | 1993 | weight / (1.028 − 0.028 × reps) | 1–10 reps |
| Average | — | Mean of Epley and Brzycki | 1–10 reps (recommended) |
Using the percentage table for strength programming
Most strength programs prescribe loads as a percentage of 1RM. At 80–85% 1RM (3–6 reps), you train the strength-hypertrophy continuum. At 70–80% (6–12 reps), hypertrophy is maximised. At 85–95% (1–5 reps), you develop maximum strength. Olympic lifters and powerlifters often train at 85–100% in peaking phases. The percentage table gives you the actual kilogram or pound target for each zone, eliminating mental arithmetic between sets.
| % of 1RM | Rep range | Primary adaptation |
|---|---|---|
| 95–100% | 1–2 | Max strength (neural) |
| 85–95% | 2–4 | Strength |
| 75–85% | 4–8 | Strength-hypertrophy |
| 67–75% | 8–12 | Hypertrophy |
| 50–67% | 12–20+ | Muscular endurance |
Glossary
- 1RM
- One-Rep Max — the maximum weight you can lift for exactly one full repetition.
- Epley formula
- A 1985 equation estimating 1RM from submaximal reps: weight × (1 + reps/30).
- Brzycki formula
- A 1993 equation estimating 1RM: weight / (1.028 − 0.028 × reps).
- Training volume
- Sets × reps × weight — a key driver of hypertrophy and strength gains.
- RPE
- Rate of Perceived Exertion — a subjective scale (1–10) used alongside percentage training to auto-regulate intensity.
Related reading
Frequently Asked Questions
Get weekly tool tips & updates
New tools, power-user tips, and productivity hacks — delivered free every Friday.
No spam, ever. Unsubscribe with one click.
Why use One Rep Max Calculator?
- Based on widely-accepted clinical and scientific formulas
- No personal data stored — all calculations run locally
- Supports both metric and imperial units
- Results include actionable recommendations
Common use cases
- Calculate BMI before a doctor's appointment
- Estimate daily calorie needs for a weight loss goal
- Track ideal body weight range for a fitness plan
- Calculate pregnancy due date
- Find out your recommended water intake based on body weight
Related Health & Fitness
Calories Burned Calculator
Calculate calories burned during any exercise or activity. Uses MET values for 30+ activities including running, cycling, swimming, and everyday tasks.
Macro Calculator
Calculate your daily macronutrients (protein, carbs, fat) for your fitness goals. Free macro calculator for weight loss, muscle gain, keto, and more.
TDEE Calculator
Calculate your Total Daily Energy Expenditure (TDEE) and get personalized calorie and macro targets for weight loss, maintenance, or muscle gain.
BMR Calculator
Calculate your Basal Metabolic Rate (BMR) using Mifflin-St Jeor, Harris-Benedict, or Katch-McArdle formula. Free online BMR calculator.
Body Fat Percentage Calculator
Calculate your body fat percentage using the US Navy or BMI method. Find your fat mass, lean mass, and fitness category. Free body fat estimator.
Ideal Weight Calculator
Calculate your ideal body weight using 4 proven formulas: Robinson, Miller, Devine, and Hamwi. Find the healthy weight range for your height.
Explore all Health & Fitness.