1RM Calculator
Estimate your one-rep max for any lift
Quick Facts
- •Most accurate with 1–10 rep sets
- •Train at 70–85% of 1RM for strength
- •Train at 60–70% for hypertrophy
What Is a One-Rep Max (1RM)?
Your one-rep max is the maximum weight you can lift for a single repetition with proper form. It is a key metric in strength training for programming training loads. Rather than testing a true 1RM (which carries injury risk), you can estimate it from submaximal lifts.
The Brzycki Formula
This calculator uses the Brzycki formula: 1RM = weight × (36 / (37 − reps)). It is most accurate for sets of 1–10 reps. For higher rep ranges, the Epley formula (weight × (1 + reps/30)) may be more accurate.
Understanding the 1rm calculator
A one-rep max is the heaviest single repetition you can complete with good form. Testing it directly is risky and tiring, so lifters estimate it from a set taken close to failure. Every formula is an approximation that gets less accurate above about eight repetitions, because endurance starts to matter more than pure strength.
Worked examples
Estimating a squat max from 5 reps at 225 lb
- 1Use the Epley formula: 1RM = weight × (1 + reps ÷ 30).
- 2Substitute: 225 × (1 + 5 ÷ 30).
- 35 ÷ 30 = 0.1667, so the multiplier is 1.1667.
- 4225 × 1.1667 = 262.5 lb.
An estimated one-rep max of about 262 lb, so round training loads to 260 lb.
Setting working weight at 75 percent of a 100 kg max
- 175 percent of 100 kg = 75 kg.
- 2The percentage chart puts 75 percent at roughly 10 repetitions.
- 3For a strength block, stop two reps short of failure and do sets of 8.
75 kg for sets of 8, leaving two repetitions in reserve.
Repetitions to percentage of one-rep max
| Reps to failure | Percent of 1RM | Training focus |
|---|---|---|
| 1 | 100% | Max strength |
| 2 | 95% | Max strength |
| 3 | 93% | Strength |
| 5 | 87% | Strength |
| 6 | 85% | Strength and size |
| 8 | 80% | Size |
| 10 | 75% | Size |
| 12 | 70% | Size and endurance |
| 15 | 65% | Endurance |
Percentages shift by lift. Most people manage more repetitions at a given percentage on the leg press than on the bench press.
Common estimation formulas
| Formula | Equation | Behaviour |
|---|---|---|
| Epley | w × (1 + r ÷ 30) | Slightly high at high reps |
| Brzycki | w ÷ (1.0278 - 0.0278r) | Accurate to about 10 reps |
| Lombardi | w × r^0.10 | Conservative |
| O'Conner | w × (1 + 0.025r) | Lowest estimates |
Practical tips
- •Estimate from a set of 3 to 6 repetitions for the closest result.
- •Re-test the estimate every four to six weeks rather than every session.
- •Bar speed on the last repetition tells you more than the number itself. If it slowed to a crawl, you were at your limit.
Frequently asked questions
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Always use a spotter when lifting heavy. This is an estimate — actual 1RM may vary.