# One-Rep Max Calculator (1RM)

URL: https://speedycalculator.com/calculators/sports/one-rep-max/
Last updated: 2026-10-25

> The one-rep max calculator estimates the most weight you could lift once from a weight lifted for several reps, using the Epley and Brzycki formulas, and gives training loads at common percentages.

## Inputs

- Weight lifted (kg, lb, g, oz, st)
- Reps completed

## Results

- Estimated 1RM (Epley)
- Estimated 1RM (Brzycki)
- 90% of 1RM
- 80% of 1RM
- 70% of 1RM

## Formula

```
Epley: 1RM = w × (1 + reps ÷ 30)
Brzycki: 1RM = w × 36 ÷ (37 − reps)
```

## Explanation

Estimating 1RM avoids risky max attempts and helps programme training intensity.

### How to use the One-Rep Max Calculator

- **Weight lifted**
- **Reps completed**

Results update as you type, and every field accepts the units shown in its menu.

### How it works

The weight and reps you can do are entered into each formula; estimates are most accurate for 10 reps or fewer.

### Inputs explained

FieldWhat to enterWeight liftedUnits: kg, lb, g, oz, stReps completedA number

### What each result means

- **Estimated 1RM (Brzycki)** = [Weight lifted]×36÷(37 - [Reps completed])
- **90% of 1RM** = [Estimated 1RM (Epley)]×0.9
- **80% of 1RM** = [Estimated 1RM (Epley)]×0.8
- **70% of 1RM** = [Estimated 1RM (Epley)]×0.7

### Example values

How the main result changes when **Weight lifted** changes and everything else stays at the example values above:

Weight lifted (kg)Estimated 1RM (Epley) (kg)404860728096100120120144160192

## Worked example

Inputs — Weight lifted: 80 kg; Reps completed: 6.

Results — **Estimated 1RM (Epley) = 96 kg**; Estimated 1RM (Brzycki) = 92.9 kg; 90% of 1RM = 86.4 kg; 80% of 1RM = 76.8 kg; 70% of 1RM = 67.2 kg.

## FAQ

**Which formula is best?**
They agree closely at low reps; at high reps all become less accurate.

**Should beginners test a true 1RM?**
It is safer to estimate from sets of 3–8 reps.

**What formula does the One-Rep Max Calculator use?**
Epley: 1RM = w × (1 + reps ÷ 30).