Planet Size Comparison

Compare mean equatorial diameters, masses, and volumes relative to Earth—interactive charts, NASA-style reference data, shareable links. All in your browser.

Size and mass values sourced from NASA Planetary Fact Sheet (Williams, 2024). All ratios are relative to Earth = 1.

By Muhammad Abdullah Rauf · Founder, EverydayTools.proUpdated 2026-05-21

What is a planet size comparison tool?

A planet size comparison tool shows mean equatorial diameters, diameter ratios versus Earth, and approximate volume ratios for Mercury through Pluto using NASA-style reference values—all calculated in your browser.

A planet size comparison tool answers how wide each world is relative to Earth—not how far it orbits the Sun. It uses mean equatorial diameters from planetary fact sheets (NASA/JPL style), converts to miles, and shows diameter ratios and sphere-model volumes (diameter cubed).

Gas giants are oblate and lack a sharp surface; published diameters are reference values suitable for classrooms, not mission geodesy. Pair this with a planet distance converter for orbital spacing and a weight-on-planets tool for surface gravity.

All math runs locally in your browser. Your selections and share URLs are not uploaded to EverydayTools servers.

Diameter ratios are linear; volume ratios scale with diameter cubed—why Jupiter is ~11× wider but ~1,300× Earth’s volume in a sphere model.

Quick answers

Concise answers for common searches — definitions, steps, and comparisons.

How many Earths fit inside Jupiter by volume?

Using mean equatorial diameters and a sphere model, Jupiter’s volume is on the order of 1,300–1,400 Earth volumes because Jupiter is about 11× wider and volume scales with diameter cubed.

Which planet is closest in size to Earth?

Venus has the closest mean diameter to Earth—only slightly smaller. Mars is about half of Earth’s width.

Is planet size the same as distance from the Sun?

No. Physical size is a world’s diameter. Orbital distance is semi-major axis in AU—use a planet distance converter for heliocentric spacing.

Mean equatorial diameter and sphere volume

Diameters follow rounded NASA Planetary Fact Sheet style means. Volume assumes a sphere: V ∝ d³ versus Earth.

Formula

Volume ratio ≈ (d_planet ÷ d_Earth)³

Assumptions

  • Spherical body with listed mean equatorial diameter
  • Gas-giant diameters are 1-bar / mean reference levels

Limitations

  • Not real-time ephemeris or oblateness-corrected geodesy
  • Pluto and small worlds deviate from perfect spheres

How to use Planet Size Comparison

  1. Pick Planet A and Planet B

    Choose any two worlds from the dropdowns—or click rows in the ranked chart (Shift+click for Planet B).

  2. Switch compare mode

    Toggle diameter, radius, volume (sphere model), or mass in Earth masses (M⊕) to see the active ratio.

  3. Read ratios and the data table

    Use the animated ratio cards and full solar-system table for diameters, volumes, gravity, and mean Sun distance.

  4. Share your comparison

    Swap planets, copy a text summary, or share the URL—the link restores your two selections.

Planet Size Comparison examples

Earth vs Jupiter diameter and volume

Input

Earth and Jupiter mean equatorial diameters

Output

Jupiter ≈ 11× wider; volume ratio on the order of 1,300+ Earth volumes (sphere model)

Volume scales with diameter cubed—why width ratios understate how much space a gas giant occupies.

Who uses Planet Size Comparison?

Common real-world scenarios where this tool saves time.

Classroom scale lessons

Show why gas giants dominate solar-system mass budgets when volume scales with diameter cubed.

Homework and science fair prep

Verify Jupiter vs Earth diameter (~11×) and volume (~1,300 Earths) with citeable NASA-style reference data.

Content and outreach

Capture shareable comparison links for blogs, newsletters, or museum kiosks without installing planetarium software.

Cross-tool solar system modules

Combine with planet distance, planetary day, weight, and age tools for size–distance–time–gravity lessons.

Workflow guides

Step-by-step chains that connect related tools for common tasks.

Classroom size–distance module

  1. Compare two planets here for diameter and sphere-model volume ratios.
  2. Open Planet Distance Converter for mean AU spacing from the Sun.
  3. Optional: use Weight on Other Planets for surface gravity at the same scale lesson.

Reference tables

Planet size vs orbital distance — what this tool covers

Physical diameter comparisons are not the same as heliocentric AU spacing.

ConceptThis toolPlanet Distance Converter
MeasuresMean equatorial diameter (km)Mean distance from Sun (AU, km)
ComparesHow wide a globe isHow far a planet’s orbit sits from the Sun
Best forJupiter vs Earth scale, Pluto vs MoonMars vs Earth orbital spacing

Use both tools together for a complete solar-system scale lesson.

Quick diameter reference (mean equatorial, rounded)

Order-of-magnitude widths for classroom context—see the live table for full values.

BodyApprox. diameterVs Earth width
Mercury~4,880 km~0.38×
Earth~12,756 km1× (reference)
Mars~6,779 km~0.53×
Jupiter~143,000 km~11.2×
Pluto~2,380 km~0.19×

Common mistakes to avoid

Assuming diameter equals visible disk in a photo

We compare mean equatorial diameters—telescope appearance also depends on distance and atmosphere.

Using orbital AU values to compare globe width

AU measures Sun distance; use this page for km/mile diameters and Earth-relative ratios.

Troubleshooting

Volume ratio seems huge for gas giants

Likely cause: Volume scales with diameter cubed.

Fix: Compare diameter ratios first, then volume—Jupiter’s volume vs Earth is dramatic by design.

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Frequently Asked Questions

What does this planet size comparison show?

Mean equatorial diameters in kilometers and miles, diameter ratios versus Earth, and approximate volume ratios (diameter cubed vs Earth) for Mercury through Pluto. It compares how wide each world is—not how far it orbits from the Sun.

Is planet size the same as distance from the Sun?

No. Orbital distance (semi-major axis) is how far a planet’s path sits from the Sun in AU or km. Physical size is the planet’s own diameter. Our Planet Distance Converter handles orbits; this page handles globe size.

Why are gas giant diameters approximate?

Jupiter, Saturn, Uranus, and Neptune are oblate and lack a sharp solid surface. Published diameters are reference values (often 1-bar atmosphere or mean spherical equivalents) suitable for classroom comparison—not millimeter-precise geodesy.

How do you get volume vs Earth?

We assume each body is a sphere with the listed mean equatorial diameter, so volume scales as diameter cubed. That is a geometry teaching shortcut—real interiors, compression, and shape differ, especially for small worlds like Pluto.

Can I share a comparison between two planets?

Yes. The URL updates with your two selections (and you can use Swap). Copy the link from your browser or use the copy-summary control on the page to grab text plus the shareable URL.

How many Earths fit inside Jupiter by volume?

Using a simple sphere model with mean equatorial diameters, Jupiter’s volume is on the order of 1,300–1,400 Earth volumes (because volume scales with diameter cubed and Jupiter is about 11× wider than Earth). The exact headline number depends slightly on which reference diameters you use—this page shows the ratio from our rounded fact-sheet values.

Which planet is closest in size to Earth?

Venus is closest in diameter—only slightly smaller than Earth. Mars is about half of Earth’s width. Mercury is smaller still. For a quick side-by-side, pick Earth and Venus in the selectors above.

Why is Uranus sometimes listed as bigger in diameter than Neptune?

Mean equatorial diameter references can differ slightly between sources and update as measurements improve; Uranus and Neptune are very close in size. Mass is a different story—Neptune is denser and more massive than Uranus even when diameters are similar.

Is Pluto smaller than Earth’s Moon?

Yes—Pluto’s mean diameter is roughly 2,380 km while the Moon is about 3,470 km across, so the Moon is noticeably wider. Pluto is still a fascinating dwarf planet for comparisons; use the table on this page to see both in context with the classical planets.

Are my selections uploaded to a server?

No. Comparisons and share URLs are processed locally in your browser. EverydayTools does not receive your planet picks or store them on a server.

Privacy, accuracy, and trust

Privacy

Planet Size Comparison (/planet-size-comparison) runs in your browser when supported—inputs are not uploaded to EverydayTools servers.

Accuracy

Size and mass values follow NASA Planetary Fact Sheet style references (Williams, 2024). Ratios are relative to Earth = 1. For mission design, use official ephemerides.

Educational astronomy only—not for navigation, spacecraft sizing, or engineering tolerances.

Part of Date & Time Tools

Related Tools

More free tools for the same workflow.

Weight on Other Planets

How much would you weigh on Mars (38% of Earth), Jupiter (2.5×), or the Moon (16.5%)? Free weight on other planets calculator using NASA surface gravity values. No signup. Runs locally in your browser when supported—no upload required for normal use.

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Reviewed by EverydayTools Editorial Team on 2026-05-21.