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Solid geometry: spheres & Platonic solids

modified2026-07-22statusfinished

Partial-fill volumes for spherical tanks, and complete edge/area/volume/sphere-radius properties for the five Platonic solids. (For toroidal rings, see the torus calculator.)

Index

Spherical tank & cap volume

[8.10] Governing equations

$$V_{\text{cap}}=\frac{\pi h^2}{3}(3R-h),\quad A_{\text{cap}}=2\pi R h,\quad V_{\text{sphere}}=\frac{4}{3}\pi R^3$$

Liquid filled to depth $h$ in a sphere of radius $R$ forms a spherical cap. Source: 1728 Software Systems & Engineering ToolBox.

h R
FIG. 01 — sphere of radius R filled to depth h (shaded cap)
Cap (liquid) volume
Percent full
Headspace volume
Wetted (curved) surface area
Full sphere volume
Full sphere surface area

Five Platonic solids

[8.12] Governing equations

$$V_{\text{tetra}}=\frac{a^3}{6\sqrt2},\quad V_{\text{cube}}=a^3,\quad V_{\text{dodec}}=\frac{15+7\sqrt5}{4}a^3$$

Surface area, volume, insphere radius $r_{\text{in}}$ and circumsphere radius $R$ of a regular solid from its edge length $a$. Source: 1728 Software Systems.

R
FIG. 02 — regular tetrahedron with its circumscribed sphere (radius R)
Surface area
Volume
Insphere radius r_in
Circumsphere radius R