Library / Foundations: Maths / FMA-11
Foundations: Maths
Sphere: volume and surface area
Volume of a sphere from its radius.
- Ref
- FMA-11
- Rev
- v1
- Field
- Foundations: Maths
- Result
- V [cm³]
r is the radius, half the diameter. Volume is in cubic units and surface area in square units.
The volume of a sphere grows with the cube of its radius: double the radius and the volume is eight times larger.
Calculator
cm³
cm
- Surface area 4πr²314.2 cm²
- Volume in litres0.5236 L
What drives the result
Each variable is moved across its typical range while the others stay at the values above. The longest bar is the key driver.
Volume (cm³) current value 523.6 cm³
rRadiusKey driver
0.524524,000
- Volume goes as r³ and surface area as r², so large spheres have less surface per unit volume.
- Use the radius, not the diameter.
Chart data as tables
Ranked variables
| Variable | Typical range | Lowest result | Highest result | Swing (cm³) | Local step | Change in result |
|---|---|---|---|---|---|---|
| r Radius | 0.5 to 50 cm | 0.5236 | 523,600 | 523,600 | +10% | +33.1 % |
Sweep of Radius
| Radius (cm) | Volume (cm³) |
|---|---|
| 0.5 | 0.5236 |
| 0.8891 | 2.944 |
| 1.581 | 16.56 |
| 2.812 | 93.11 |
| 5 | 523.6 |
| 8.891 | 2,944 |
| 15.81 | 16,560 |
| 28.12 | 93,110 |
| 50 | 523,600 |
Sweep one variable
Volume (cm³)Hover, touch, or use the arrow keys on the chart
Variables and how each one contributes
V
Volume
What the equation gives you. Everything else feeds it.
r
Radius
Distance from the centre to the surface. Cubed: +10% radius gives +33% volume.
Worked example with the values above
- Cube the radius: 5³ = 125.
- Multiply by 4π/3 ≈ 4.18879.
- V = 523.6 cm³.
Assumptions and limits
- A perfect sphere.
- Radius in the same unit as the volume.
Common mistakes
- Using the diameter.
- Squaring instead of cubing.
Statistics and uncertainty
The cube amplifies errors by three: δV/V = 3δr/r. A 1% error in diameter gives a 3% error in volume.
Where it is used
- Tank and balloon volumes.
- Mass of spherical shot from density.
Maths you need
- Cubes: r³
- Pi: ≈ 3.14159