# One-rep max calculator

> One-rep max (1RM) from a set of reps with the Epley, Brzycki, Lombardi and O'Conner equations, plus training loads from 50 % to 100 %.

직접 계산할 수 있는 페이지: https://www.calcopenly.com/ko/health/one-rep-max-calculator
분야: 건강 및 피트니스 계산기

A one-rep max (1RM) is the heaviest load you can lift once with good form. It is estimated here from a set taken to failure with four equations: Epley, weight × (1 + reps ÷ 30); Brzycki, weight × 36 ÷ (37 − reps); Lombardi, weight × reps^0.10; and O'Conner, weight × (1 + 0.025 × reps). The main result is their mean, shown in kilograms and pounds.

Lifters use it to set training loads without a maximal attempt. With the default 100 kg for 5 reps, the four equations give 112.5 to 117.5 kg and a mean of 114.8 kg; the table then lists loads from 50 % to 100 % of that, with the reps Epley predicts at each.

The equations were fitted to groups of lifters and lose accuracy as reps rise, especially past 10. They are lift-specific, so an estimate from the bench press says nothing about the squat.

## 입력

- **Weight lifted**
- **Reps completed**: Clean reps to failure in one set

## 결과

- Estimated one-rep max (mean of four) (kg) — 주요 결과
- Estimated one-rep max in pounds (lb)
- Epley (kg)
- Brzycki (kg)
- Lombardi (kg)
- O'Conner (kg)

## 공식

$$
\text{Epley } w\left(1 + \tfrac{r}{30}\right) \quad \text{Brzycki } w\,\tfrac{36}{37 - r} \quad \text{Lombardi } w\,r^{0.10} \quad \text{O'Conner } w(1 + 0.025r)
$$

## 계산 예제

### 100 kg for 5 reps

- Weight lifted: 100 kg
- Reps completed: 5
- **Epley: 116.7 kg**
- **Brzycki: 112.5 kg**
- **Lombardi: 117.5 kg**
- **O'Conner: 112.5 kg**
- **Estimated one-rep max (mean of four): 114.8 kg**
- 검증 출처: Python 3.8 decimal/math: 100(1 + 5/30), 100·36/32, 100·5^0.1, 100(1 + 0.125); mean of the four

### 225 lb for 10 reps

- Weight lifted: 225 lb
- Reps completed: 10
- **Epley: 136.1 kg**
- **Lombardi: 128.5 kg**
- **Estimated one-rep max (mean of four): 132.1 kg**
- **Estimated one-rep max in pounds: 291.1 lb**
- 검증 출처: Python 3.8 decimal: 225 lb = 102.0582833 kg; Epley 300 lb = 136.0777 kg; Lombardi 225·10^0.1 lb; mean 291.127 lb

### A single rep is already a 1RM

- Weight lifted: 140 kg
- Reps completed: 1
- **Estimated one-rep max (mean of four): 140.0 kg**
- **Epley: 140.0 kg**
- **O'Conner: 140.0 kg**
- 검증 출처: Convention stated in the steps: r = 1 returns the lifted weight for every equation (Brzycki and Lombardi give it exactly)

### 60 kg for 12 reps

- Weight lifted: 60 kg
- Reps completed: 12
- **Epley: 84.0 kg**
- **Brzycki: 86.4 kg**
- **Lombardi: 76.9 kg**
- **O'Conner: 78.0 kg**
- **Estimated one-rep max (mean of four): 81.3 kg**
- 검증 출처: Python 3.8 decimal/math: 60·1.4, 60·36/25, 60·12^0.1, 60·1.3; mean 81.3313

## 자주 묻는 질문

### How do you calculate your one-rep max?

Lift a weight for as many clean reps as possible in one set, then apply an equation. Epley's is weight × (1 + reps ÷ 30), so 100 kg for 5 reps gives 116.7 kg; Brzycki's is weight × 36 ÷ (37 − reps), giving 112.5 kg. This calculator averages Epley, Brzycki, Lombardi and O'Conner, which gives 114.8 kg for that set.

### Which one-rep max formula is most accurate?

None is best for every lift or lifter, and they agree most at low reps. For 100 kg lifted 5 times the four span 112.5 to 117.5 kg, a 5 kg spread; for 60 kg lifted 12 times they span 76.9 to 86.4 kg, almost 10 kg. Estimates from sets of 10 reps or fewer are therefore more consistent, and the mean used here sits between the highest and lowest equation.

### How many reps can you do at 80 % of your one-rep max?

About 8, by the Epley equation solved for reps: 30 × (100 ÷ 80 − 1) = 7.5, rounded to 8. The table under the result lists loads and Epley rep estimates from 50 % to 100 %: at 90 % it gives 3 reps and at 70 % it gives 13. Real rep counts at a given percentage vary between lifts and between lifters.

### “One-rep max calculator”의 정확도는 어느 정도인가요?

정확도는 입력값과 계산 방법의 가정에 따라 달라집니다. 십진 연산은 유효숫자 50자리를 사용하지만, 추정값·수치해석 방법·원본 데이터의 정밀도는 더 낮을 수 있습니다. 표시값을 반올림해도 이러한 한계는 사라지지 않습니다. 독립적인 출처의 풀이와 대조한 계산 예시: 4. 예를 들어 “100 kg for 5 reps”은 Python 3.8 decimal/math: 100(1 + 5/30), 100·36/32, 100·5^0.1, 100(1 + 0.125); mean of the four와 대조해 확인합니다.

### 이 계산 방법의 출처는 무엇인가요?

LeSuer DA, McCormick JH, Mayhew JL, Wasserstein RL, Arnold MD. The accuracy of prediction equations for estimating 1-RM performance in the bench press, squat, and deadlift. J Strength Cond Res 1997;11(4):211–213; Brzycki M. Strength testing — predicting a one-rep max from reps-to-fatigue. J Phys Educ Recreat Dance 1993;64(1):88–90; Epley B. Poundage chart. Boyd Epley Workout. Lincoln, NE: Body Enterprises; 1985.

## 출처

- LeSuer DA, McCormick JH, Mayhew JL, Wasserstein RL, Arnold MD. The accuracy of prediction equations for estimating 1-RM performance in the bench press, squat, and deadlift. J Strength Cond Res 1997;11(4):211–213
- [Brzycki M. Strength testing — predicting a one-rep max from reps-to-fatigue. J Phys Educ Recreat Dance 1993;64(1):88–90](https://doi.org/10.1080/07303084.1993.10606684)
- Epley B. Poundage chart. Boyd Epley Workout. Lincoln, NE: Body Enterprises; 1985