Solar system scale model: sizes and distances on two scales
Choose how big the Sun is in the model and see what the planets become, then separately how far Earth sits from it. Orbits keep their real shape, and the spheres for printing download as STL.
Opens without an account 3 times a day. A free account removes the limit.
- 2 separate scalessize and distance
- 11 bodiesSun, 8 planets, Moon, Pluto
- 1 to 11,728distance to the Sun against Earth's diameter
- STLspheres at the size scale
What a solar system scale model is
A solar system scale model is a free online tool from EduFacturing that shows why the solar system cannot be drawn on one scale, and gives two separate ones: for the sizes of the bodies and for the distances between them. The number behind it is 149,597,870.7 km (one astronomical unit) against 12,756 km (Earth's diameter): about 11,728.
The two scale tables also show the trap: at the size scale how far away the orbits end up, at the distance scale how small the planets become. Everything is calculated in the browser.
Planet sizes and distances
Planet sizes to scale
Choose the Sun: a marble of 1.5 cm, a football of 22 cm, a basketball of 24 cm, or your own value. The table gives the model diameter of 11 bodies and the distance of the planets, the Moon and Pluto at the same scale. With a 22 cm Sun, Earth is 2.017 mm and Neptune is 711.44 m away.
Distances between planets to scale
Place Earth at 10 cm, 1 m, 10 m or your own value. The table gives the semi-major axis of 8 planets in AU and in the model. With Earth at 1 m, Neptune is 30.07 m away and Earth is 0.085 mm.
Orbits with their real shape
The diagram draws the real eccentricities with the Sun at the focus. The table gives e, perihelion, aphelion, inclination and period; Pluto's orbit is optional.
STL of the spheres for printing
Download one globe or a set of chosen bodies at the size scale. Bodies under 0.8 mm for FDM are flagged.
When you need a solar system model to scale
One scale never fits, and that is the lesson.
An astronomy lesson
A teacher asks where Earth is if the Sun is a football. The table answers: a 2 mm grain 23.66 m away.
A walk in the yard
The class paces out the distances: with Earth 1 m from the Sun, Jupiter is 5.20 m away and Neptune 30.07 m.
Printed globes
The Sun and planets print at one scale so their sizes can be compared: with a 22 cm Sun, Jupiter is 2.26 cm and Earth 2.017 mm.
Physics and maths
Eccentricity, perihelion, aphelion, inclination and period from a table of NASA data, instead of a picture with an exaggerated ellipse.
How the scale is worked out
A scale is a factor K: the model length is the real length divided by K. The two scales are independent and are never drawn together.
Choosing the scale
You choose the Sun's diameter in mm or the Earth-Sun distance in mm. K follows from the choice, and every body is calculated with it.
Orbit
An ellipse is built from a and e, and the Sun goes at the focus, a·e from the centre. Perihelion is a·(1 − e), aphelion a·(1 + e).
STL
Spheres take their diameters from the size scale, with 24 segments, in a row 4 mm apart.
| Applies to | Formula | Meaning |
|---|---|---|
| Size scale | mm = km · 1,000,000 / K | K = 1,391,000 · 1,000,000 / the Sun's diameter in mm; with 22 cm, K = 6,322,727,273 |
| Distance scale | mm = AU · 149,597,870.7 · 1,000,000 / K | K = 149,597,870.7 · 1,000,000 / the Earth-Sun distance in mm |
| Distance to size | 149,597,870.7 / 12,756 ≈ 11,728 | with Earth at 5 mm, the Sun is 58.6 m away |
Orbits with their real shape, sourced numbers
Two scales, kept apart
The two scale tables also show the wrong side of the scale, for example Neptune 711.44 m away with a 22 cm Sun.
Orbits use the real eccentricities
Earth has e = 0.0167, so the diagram is almost round, and the Sun sits at the focus of each ellipse, not in the middle.
The numbers have a source
Diameters, semi-major axes, eccentricities, periods and inclinations follow the NASA Planetary Fact Sheet data, rounded; the AU is exact by the 2012 IAU definition. The tests check the data against Kepler's third law.
There is no animation and no positions of the planets over time: orbits are flat shapes, and inclination (7.005° for Mercury, 17.16° for Pluto) is only in the table. The Moon is in the size scale but has no orbit, and the distance scale holds only the eight planets.
The STL is spheres only, with no rings for Saturn. With a 1.5 cm Sun six of the eight planets are under 0.8 mm for FDM, and with 22 cm only Mercury, the Moon and Pluto; the spacing between spheres in a set is not to scale.
Questions about the solar system scale model
How big is the Sun in the model?
You choose: a marble of 1.5 cm, a football of 22 cm, a basketball of 24 cm, or your own value. With a 22 cm Sun, Earth is 2.017 mm and Jupiter 2.26 cm.
Why can't the solar system be drawn to scale?
The ratio is 149,597,870.7 km to 12,756 km, about 11,728. With Earth at 5 mm the Sun is 58.6 m away, and with Earth 1 m from the Sun Earth itself is 0.085 mm. So there are two scales.
What is an astronomical unit and why is it such a precise number?
It is the Earth-Sun distance. Since 2012 it is a definition, not a measurement: exactly 149,597,870.7 km by decision of the International Astronomical Union.
How far is Earth from the Sun in the model?
With a Sun the size of a 22 cm football, Earth is a 2 mm grain 23.66 m away.
Can the model be printed?
Yes, by size: spheres in STL. The spacing between spheres in a set is not to scale: with Earth at 1 mm, Neptune would be 352.6 m away.
How much does the solar system scale model cost?
It is free. The tool opens without an account 3 times a day, and a free account removes the limit.
The solar system scale model is free. Pro opens the rest
Pro costs 15 EUR a month and opens 45 Pro tools.
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