🏋️ One Rep Max Calculator
Estimate the most you could lift for a single rep from a set of several reps – no maximal attempt needed.
Quick answer: Epley 1RM = weight × (1 + reps ÷ 30). Lifting 100 kg for 5 reps gives an estimated 1RM of 116.7 kg (Epley), 112.5 kg (Brzycki) and 117.5 kg (Lombardi) – an average of 115.5 kg.
Updated · Free · No sign-up · Works on any device
One Rep Max Calculator inputs
Result
Estimated one-rep max
115.5 kg
Average of three formulas from 100 kg × 5
| Epley | 116.7 kg |
| Brzycki | 112.5 kg |
| Lombardi | 117.5 kg |
| Average | 115.5 kg |
Training percentages
| % of 1RM | Weight | Approx. reps |
|---|---|---|
| 100% | 115.5 kg | 1 |
| 95% | 109.7 kg | 2 |
| 90% | 104 kg | 3 |
| 85% | 98.2 kg | 5 |
| 80% | 92.4 kg | 8 |
| 75% | 86.6 kg | 10 |
| 70% | 80.9 kg | 13 |
| 65% | 75.1 kg | 16 |
| 60% | 69.3 kg | 20 |
| 55% | 63.5 kg | 25 |
| 50% | 57.8 kg | 30 |
How one-rep max is estimated
The heavier the weight, the fewer reps you can do. Researchers have fitted formulas to that relationship, so a set of several reps to near-failure predicts your single-rep maximum.
Epley: 1RM = w × (1 + r ÷ 30) · Brzycki: 1RM = w × 36 ÷ (37 − r) · Lombardi: 1RM = w × r0.10
Here w is the weight lifted and r the number of reps completed. With one rep, the 1RM is simply the weight lifted.
Worked example
A lifter benches 100 kg for 5 reps. Epley: 100 × (1 + 5/30) = 116.7 kg. Brzycki: 100 × 36 ÷ 32 = 112.5 kg. Lombardi: 100 × 50.1 = 117.5 kg. The average estimate is 115.5 kg, so a 3 × 5 at 80% would use about 92.4 kg.
Percentage guide
| % of 1RM | Typical reps | Training goal |
|---|---|---|
| 90–100% | 1–3 | Maximal strength |
| 80–90% | 3–6 | Strength |
| 65–80% | 6–12 | Muscle growth (hypertrophy) |
| 50–65% | 12–20+ | Muscular endurance, technique |
Tips
- Use a set taken within one or two reps of failure with good form.
- Keep reps between 2 and 10 for the most reliable estimate.
- Estimates differ between lifts – calculate each exercise separately.
- Always use a spotter or safety bars for heavy pressing and squatting.
Tracking strength over time
Your estimated 1RM is a convenient way to compare progress across different rep ranges. Log the weight and reps of your top working set each week; if the estimated maximum keeps rising, your training is working even if you never attempt a true single. Recalculate your training percentages every four to six weeks as you get stronger.
For general information only – not medical advice. Consult a healthcare professional.
Frequently asked questions
How accurate are 1RM calculators?
They are usually within about 5% for sets of 2–10 reps taken close to failure. Accuracy drops with higher reps, and results vary by lift and by how trained you are.
Which 1RM formula is best?
Epley and Brzycki are the most widely used and agree closely around 10 reps. Brzycki tends to be more conservative at low reps; averaging several formulas smooths out their differences.
Is it safe to test my true one-rep max?
Maximal attempts carry more injury risk, especially without a spotter or good technique. Estimating from a 3–5 rep set is a safer way to track strength for most people.
How do I use 1RM percentages in training?
Strength work is typically done at 80–90% of 1RM for 3–6 reps, muscle building at 65–80% for 6–12 reps, and muscular endurance below 65% for 12+ reps.