# Simple Pendulum Calculator

URL: https://speedycalculator.com/calculators/physics/pendulum/
Last updated: 2026-10-25

> The pendulum calculator finds the period and frequency of a simple pendulum from its length, T = 2π√(L ÷ g). Type a period to find the length needed.

## Inputs

- Length (m, cm, mm, km, in, ft, yd, mi)
- Gravitational acceleration (m/s², ft/s², g)

## Results

- Period
- Frequency

## Formula

```
T = 2π √(L ÷ g)
```

## Explanation

For small swings, a pendulum’s period depends only on its length and gravity, not its mass, which made pendulum clocks possible.

### How to use the Simple Pendulum Calculator

- **Length**
- **Gravitational acceleration**
- Want to work backwards? Type a value into **Period** and **Length** is calculated for you.

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

### How it works

Divide length by gravitational acceleration, take the square root and multiply by 2π.

### Inputs explained

FieldWhat to enterLengthUnits: m, cm, mm, km, in, ft …Gravitational accelerationUnits: m/s², ft/s², g

### What each result means

- **Period** = 2×pi×sqrt([Length]÷[Gravitational acceleration])
- **Frequency** = 1÷[Period]

### Example values

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

Length (m)Period (s)0.51.41870.751.737612.00641.252.24321.52.457322.8375

## Worked example

Inputs — Length: 1 m; Gravitational acceleration: 9.80665 m/s².

Results — **Period = 2.0064 s**; Frequency = 0.4984 Hz.

## FAQ

**How long is a seconds pendulum?**
About 0.994 m, giving a 2-second period.

**Is the formula exact?**
It assumes small angles, under about 15°.

**What formula does the Simple Pendulum Calculator use?**
T = 2π √(L ÷ g).

**Can I work backwards from the result?**
Yes. Type the result you want into Period and the calculator finds the matching length.