Plan a solar system scale model that really fits
This solar system scale model calculator works out how big to make the Sun and each planet, and how far apart to put them, so that sizes and distances use the same scale. Tell it the length of your school field, playground or corridor, or the size of the ball you have for the Sun, or the size of your Earth, or type a ratio such as 1 : 1 billion. It returns the scale, every planet’s model diameter with an everyday object of about that size, its distance from the Sun and the gap from the planet before it.
The figures are the NASA Planetary Fact Sheet values, so the table is suitable for a class project or a science fair. Print it or save it as a PDF to take outside, or download it as a CSV file for a spreadsheet. Metric and imperial units are both supported.
How to use the Solar System Scale Model Calculator
- Choose how to set the scale: Field length, Sun size, Earth size or Ratio 1 : N.
- Type the number and pick its unit, for example 100 metres for a football field or 30 cm for a beach-ball Sun.
- Tick Include Pluto if you want the dwarf planet at the far end, and choose metric or imperial results.
- Read the scale and the summary, then the table of model sizes, distances and gaps.
- Press Print or save as PDF for a handout, or Download CSV to edit the numbers.
Solar System Scale Model Calculator features
Four ways to set the scale
Fit the outermost planet to a length, start from the Sun or Earth size, or type 1 : N.
Sizes you can picture
Each model planet is compared with a pinhead, peppercorn, pea, marble, golf ball or football.
Gaps for pacing out
The distance from the previous planet tells you how far to walk between markers.
The Moon and the nearest star
The Moon’s size and distance from Earth, and how far away Proxima Centauri would be.
Printable and exportable
A print layout without the controls, plus a CSV file.
Why a true-scale model surprises everyone
Textbook pictures squeeze the planets together, because a true scale does not fit on a page. If Neptune sits at the end of a 100 m field the Sun is just 3 cm across, the size of a large grape, and Earth is a 0.28 mm speck 3.3 m away from it. If you start from a 1 m Sun instead, Earth is a 9 mm pea 107 m away, Jupiter a 10 cm grapefruit 560 m away, and Neptune is 3.2 km from the Sun. Proxima Centauri, the nearest star, would be more than 28,000 km away on that scale — further than the Earth is wide. So most schools build two models: one for sizes (big balls side by side) and one for distances (tiny beads spread out), or they accept that the planets are specks on a long walk.
How the numbers are worked out
Every length is multiplied by one scale factor k. In field mode k = field length ÷ real distance of the outermost planet; in Sun mode k = your Sun’s diameter ÷ 1,391,400 km; in Earth mode k = your Earth’s diameter ÷ 12,756 km. The scale ratio is 1 : 1/k. Model diameter = real diameter × k and model distance = mean distance from the Sun × k. Worked example for a 100 m field: k = 100 m ÷ 4,515 million km, so the scale is 1 : 45.15 billion; Earth’s distance 149.6 million km becomes 149.6 ÷ 4,515 × 100 = 3.31 m.
| Body | Diameter (km) | Mean distance from Sun (million km) |
|---|---|---|
| Sun | 1,391,400 | — |
| Mercury | 4,879 | 57.9 |
| Venus | 12,104 | 108.2 |
| Earth | 12,756 | 149.6 |
| Mars | 6,792 | 228.0 |
| Jupiter | 142,984 | 778.5 |
| Saturn | 120,536 | 1,432.0 |
| Uranus | 51,118 | 2,867.0 |
| Neptune | 49,528 | 4,515.0 |
| Pluto | 2,376 | 5,906.4 |
Tips for building the model
- Use a measuring wheel or count paces (about 0.75 m each for an adult) using the gap column.
- Mount pinhead planets on cards or lollipop sticks so they can be found again.
- Planets are never lined up like this; for a realistic layout, spread them around the Sun at today’s positions with the planets visible tonight page, or explain that the line is for distance only.
- Ask how long light, a car or a probe would take to cross the real gaps with the space travel time calculator.
Solar System Scale Model Calculator FAQ
How big is Earth if the Sun is a football?
With a 22 cm football Sun, Earth is about 2 mm across (a pinhead) and 23.7 m away; Neptune is 714 m away.
How far apart should the planets be in a school solar system model?
Set the field length and read the gap column. For a 100 m field the four inner planets all lie within about 5 m of the Sun, and the gaps grow to more than 30 m in the outer solar system.
What scale is a 1 : 1 billion solar system?
The Sun is a 1.39 m ball, Earth a 12.8 mm marble 150 m away, and Neptune 4.5 km away.
Can sizes and distances fit on one sheet of paper?
No. If the Sun-to-Neptune distance fits on an A4 page, Earth is less than a thousandth of a millimetre wide, far too small to print.
Where do the planet sizes and distances come from?
From the NASA Planetary Fact Sheet: equatorial diameters and mean distances from the Sun (the semi-major axis of each orbit).
Should I include Pluto?
It is optional. Pluto is a dwarf planet; tick the box and it becomes the far marker of the model.