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Astronomical Unit Calculator

Convert astronomical distances between astronomical units, light-years, parsecs, and familiar metric or imperial units.

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Quick Summary

Use this when you need:

Compare orbital distances in kilometers, astronomical units, and light minutes
Convert deep space measurements between parsecs and light years
Explain Solar System scale to students using familiar metric lengths

You’ll get:Distance

How this is calculated

Formula:

distance_target = distance_source * (source_to_meters / target_to_meters)

In plain language:

We route every value through meters (the base unit), so the calculator multiplies by the source to meter factor, then divides by the target to meter factor.

The formula is always visible so you can verify the math and explain your numbers to anyone who asks.

What these terms mean

Distance

Distance used in the calculation.

When to use this calculator

Compare orbital distances in kilometers, astronomical units, and light minutes
Convert deep space measurements between parsecs and light years
Explain Solar System scale to students using familiar metric lengths

Last updated: November 18, 2025

Astronomical unit calculator explained

Distances in the Solar System sound friendly when you quote astronomical units (AU), but interstellar missions still mix kilometers, light-minutes, light-years, and parsecs. Our Astronomical Unit Calculator normalizes every value into meters, then hands back whichever astronomical or terrestrial unit you need to brief a classroom, size a Hohmann transfer, or translate a press release into something a neighbor can picture.

Use it to compare orbit radii, convert light travel time into kilometers, or frame deep-space probe telemetry in the right unit system for each audience.

How the conversion works

The calculator follows the IAU definition of the astronomical unit: $1\,\text{AU} = 149\,597\,870\,700\,\text{m}$ . Every conversion simply routes through meters:

\text{target} = \text{source} \times \frac{k_\text{source}\,\text{m}}{k_\text{target}\,\text{m}}

AU → kilometers: multiply by 149,597,870.7.
Light-year → AU: multiply by $9.4607\times10^{15}$ m, then divide by the AU constant.
Parsecs → light-years: multiply by 3.26156, or divide by $206{,}264.806$ to reach AU.

Because everything reduces to meters, you can also compare to nautical miles, Earth radii, or solar radii without juggling separate formulas.

Units and conversions

Unit	Symbol	Relation
Astronomical unit	AU	$1\,\text{AU} = 149{,}597{,}870{,}700\,\text{m}$
Light-minute	lm	$1\,\text{lm} = c \times 60\,\text{s} = 17\,987\,547\,480\,\text{m}$
Light-year	ly	$1\,\text{ly} = 9.46073 \times 10^{15}\,\text{m} = 63{,}241\,\text{AU}$
Parsec	pc	$1\,\text{pc} = 3.08568 \times 10^{16}\,\text{m} = 206{,}264.806\,\text{AU}$
Earth radius	R⊕	$1\,R_\oplus = 6\,371\,000\,\text{m}$
Solar radius	R☉	$1\,R_\odot = 695\,700\,000\,\text{m}$

Worked examples

Planetary orbital comparison
How far is 1.3 AU in kilometers?

\text{km} = 1.3\,\text{AU} \times 149{,}597{,}870.7 = 194{,}477{,}231.9\,\text{km}

Result: a Mars aphelion-style orbit roughly 194 million kilometers from the Sun.

Interstellar probe framing
Convert 0.2 light-years into AU to describe Voyager 1's future milestone.

\text{AU} = 0.2\,\text{ly} \times \frac{9.46073 \times 10^{15}\,\text{m}}{149{,}597{,}870{,}700\,\text{m}} \approx 12{,}648\,\text{AU}

Result: Voyager 1 would need to travel another 12,600 AU (about 0.2 light-years) to reach that distance, emphasizing how far interstellar scales extend beyond the heliosphere.

Tips and pitfalls

Reference AU for intra-Solar-System planning, but switch to light-minutes when coordinating communications delays.
Always specify whether you use mean, perihelion, or aphelion distances when comparing planetary orbits—the calculator outputs exact scalar conversions, not orbital ranges.
Parsecs grow from parallax measurements; confirm whether your astrophysics source quotes parsecs or megaparsecs before copying numbers into mission docs.
When communicating with the public, pair AU outputs with kilometers or Earth-radii so the figure still lands.

References and further reading

Frequently Asked Questions

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Calculator info

Version:: v1.0.0
Sensitivity:: low
References:: 2

Last updated: November 18, 2025

Astronomical unit calculator explained

Use it to compare orbit radii, convert light travel time into kilometers, or frame deep-space probe telemetry in the right unit system for each audience.

How the conversion works

The calculator follows the IAU definition of the astronomical unit: $1\,\text{AU} = 149\,597\,870\,700\,\text{m}$ . Every conversion simply routes through meters:

\text{target} = \text{source} \times \frac{k_\text{source}\,\text{m}}{k_\text{target}\,\text{m}}

AU → kilometers: multiply by 149,597,870.7.
Light-year → AU: multiply by $9.4607\times10^{15}$ m, then divide by the AU constant.
Parsecs → light-years: multiply by 3.26156, or divide by $206{,}264.806$ to reach AU.

Because everything reduces to meters, you can also compare to nautical miles, Earth radii, or solar radii without juggling separate formulas.

Units and conversions

Unit	Symbol	Relation
Astronomical unit	AU	$1\,\text{AU} = 149{,}597{,}870{,}700\,\text{m}$
Light-minute	lm	$1\,\text{lm} = c \times 60\,\text{s} = 17\,987\,547\,480\,\text{m}$
Light-year	ly	$1\,\text{ly} = 9.46073 \times 10^{15}\,\text{m} = 63{,}241\,\text{AU}$
Parsec	pc	$1\,\text{pc} = 3.08568 \times 10^{16}\,\text{m} = 206{,}264.806\,\text{AU}$
Earth radius	R⊕	$1\,R_\oplus = 6\,371\,000\,\text{m}$
Solar radius	R☉	$1\,R_\odot = 695\,700\,000\,\text{m}$

Worked examples

Planetary orbital comparison
How far is 1.3 AU in kilometers?

\text{km} = 1.3\,\text{AU} \times 149{,}597{,}870.7 = 194{,}477{,}231.9\,\text{km}

Result: a Mars aphelion-style orbit roughly 194 million kilometers from the Sun.

Interstellar probe framing
Convert 0.2 light-years into AU to describe Voyager 1's future milestone.

\text{AU} = 0.2\,\text{ly} \times \frac{9.46073 \times 10^{15}\,\text{m}}{149{,}597{,}870{,}700\,\text{m}} \approx 12{,}648\,\text{AU}

Result: Voyager 1 would need to travel another 12,600 AU (about 0.2 light-years) to reach that distance, emphasizing how far interstellar scales extend beyond the heliosphere.

Tips and pitfalls

Reference AU for intra-Solar-System planning, but switch to light-minutes when coordinating communications delays.
Always specify whether you use mean, perihelion, or aphelion distances when comparing planetary orbits—the calculator outputs exact scalar conversions, not orbital ranges.
Parsecs grow from parallax measurements; confirm whether your astrophysics source quotes parsecs or megaparsecs before copying numbers into mission docs.
When communicating with the public, pair AU outputs with kilometers or Earth-radii so the figure still lands.

Quick Summary

Calculator Tool

How this is calculated

What these terms mean

Distance

When to use this calculator

Astronomical unit calculator explained

How the conversion works

Units and conversions

Worked examples

Tips and pitfalls

References and further reading

Frequently Asked Questions

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Was this calculator helpful?

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Calculator info

Astronomical unit calculator explained

How the conversion works

Units and conversions

Worked examples

Tips and pitfalls

References and further reading

Frequently Asked Questions

Related Calculators

Acreage Calculator

Acres to Hectares Converter

Acres to Square Feet Converter

Angle Conversion Calculator

Angstrom to nm converter

Area Converter

Was this calculator helpful?

Found an error?

Calculator info