One-rep max calculator
Your one-rep max (1RM) is the most weight you can lift for a single repetition. To estimate it without a risky max attempt, enter a weight and the reps you completed — this calculator applies the Epley and Brzycki formulas and shows the loads for every training percentage.
Training percentages
What to load for a given intensity, based on your estimated 1RM.
| % of 1RM | Load | ~Reps |
|---|---|---|
| 100% | 117 kg | 1 |
| 95% | 111 kg | 2 |
| 90% | 105 kg | 4 |
| 85% | 99 kg | 6 |
| 80% | 93 kg | 8 |
| 75% | 88 kg | 10 |
| 70% | 82 kg | 12 |
| 65% | 76 kg | 16 |
| 60% | 70 kg | 20 |
How it works
Rep-based 1RM estimates come from a simple relationship: the more reps you can do with a given weight, the higher your true max. The Epley equation expresses that as 1RM = weight × (1 + reps ÷ 30).
The Brzycki equation — 1RM = weight × 36 ÷ (37 − reps) — gives a close second opinion; this tool shows both and their average. Estimates are most reliable at 1–6 reps and become rougher as reps climb.
Frequently asked questions
What is a one-rep max (1RM)?
Your one-rep max is the heaviest weight you can lift for a single, full repetition of an exercise. It is the standard measure of maximal strength and the reference point most training programs use to set working weights (e.g. '3 sets of 5 at 80% of 1RM').
How is 1RM calculated from reps?
The most common estimate is the Epley formula: 1RM = weight × (1 + reps ÷ 30). For example, 100 kg for 5 reps estimates a 1RM of 100 × (1 + 5/30) ≈ 117 kg. The Brzycki formula (1RM = weight × 36 ÷ (37 − reps)) gives a similar number and is often averaged with Epley.
How accurate is an estimated 1RM?
Rep-based estimates are most accurate at low reps (1–5) and drift as reps climb, because endurance and technique increasingly affect how many reps you can grind out. Above ~10 reps treat the number as a ballpark. For the closest estimate, use a set taken close to failure at 3–6 reps.
Should I actually test my 1RM in the gym?
You don't need to. A true max attempt carries higher injury and fatigue risk, especially without a spotter or for beginners. Estimating your 1RM from a hard set of 3–6 reps gives you everything you need to program your training, safely.
What are training percentages used for?
Once you know your 1RM, percentages let you pick the right load for a goal: roughly 85–100% for strength (1–6 reps), 67–85% for hypertrophy (6–12 reps), and below 67% for muscular endurance (15+ reps). The table on this page maps your estimated 1RM onto those percentages.
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