# Parallax Calculator

URL: https://speedycalculator.com/calculators/physics/parallax/
Last updated: 2026-10-30

> The parallax calculator converts a star's annual parallax angle into its distance in parsecs and light-years, or the distance into the parallax, with values for well-known nearby stars.

## Inputs

- Find
- Star
- Parallax angle p (arcsec, mas, °)
- Distance (pc, ly, au)

## Results

- Distance
- Parallax angle
- In milliarcseconds

## Formula

```
d (pc) = 1 / p (arcsec)
```

## Explanation

As Earth orbits the Sun, nearby stars shift slightly against distant ones. This parallax angle is tiny – Proxima Centauri's is under one arcsecond – but measuring it gives the most direct distances in astronomy. The Gaia satellite has measured it for over a billion stars.

### How to use the Parallax Calculator

- **Find**
- **Star**
- **Parallax angle p**
- **Distance**

Results update as you type, every field has its own unit menu, and everything is calculated in your browser.

### How it works

Choose a star or enter the parallax in arcseconds (or milliarcseconds), or switch to find the parallax of a given distance.

### Inputs explained

FieldWhat to enterFindChoose one: Distance from parallax, Parallax from distanceStarChoose one: Proxima Centauri, Alpha Centauri A, Barnard's Star, Sirius …Parallax angle pUnits: arcsec, mas, °DistanceUnits: pc, ly, au

### What each result means

- **Distance** = 1÷[p]
- **Parallax angle** = [p]
- **In milliarcseconds** = [p]×1000

### Example values

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

Parallax angle p (arcsec)Distance (pc)0.051.30120.0751.30120.11.30120.1251.30120.151.30120.21.3012

## Worked example

Inputs — Find: Distance from parallax; Star: Proxima Centauri.

Results — **Distance = 1.301236 pc**; In milliarcseconds = 768.5 mas.

## Key terms

- **Arcsecond**: 1/3600 of a degree.

## FAQ

**What is a parsec?**
The distance at which the parallax is 1 arcsecond (3.26 ly).

**Why can't parallax measure distant galaxies?**
The angle becomes too small to measure.

**Which star has the largest parallax?**
Proxima Centauri, about 0.768″.

**How accurate is Gaia?**
Down to about 10–20 microarcseconds for bright stars.


## Sources

- [OpenStax – Astronomy 2e](https://openstax.org/details/books/astronomy-2e)
- [ESA – Gaia mission](https://www.esa.int/Science_Exploration/Space_Science/Gaia)