← Home & Construction Calculators
VOLUME3 SHAPESUNIT CONVERSION
Calculate cubic feet for boxes, cylinders or spheres, with automatic conversions, multiple-item totals, allowance and optional cost.
Volume symbols and meaning
Three-dimensional space inside or occupied by an object.
Longest box dimension.
Second box dimension.
Vertical box or cylinder dimension.
Half the cylinder or sphere diameter.
Cubic feet formulas
Box: V = L × W × H
Cylinder: V = π × r² × H
Sphere: V = (4 ÷ 3) × π × r³
Adjusted total = V × quantity × (1 + allowance ÷ 100)
All entered dimensions are first converted to feet. Applying the geometric formula after conversion prevents mixed-unit errors and produces cubic feet directly.
Visual guide to volume dimensions
Cubic units measure volume, not area. A dimension conversion must therefore be cubed: one cubic yard equals 27 cubic feet, while one cubic foot equals 1,728 cubic inches.
Worked examples
Rectangular box
A space measuring 10 ft × 8 ft × 6 ft has:
V = 10 × 8 × 6 = 480 ft³
Cylinder
A cylinder with a 4-foot diameter and 6-foot height has a 2-foot radius:
V = π × 2² × 6 = 75.40 ft³
Measurements in inches
A 24 × 18 × 12-inch box contains 5,184 in³. Divide by 1,728 to get 3 ft³.
Useful cubic-foot conversions
| 1 cubic foot equals | Value |
|---|---|
| Cubic inches | 1,728 in³ |
| Cubic yards | 0.037037 yd³ |
| Cubic meters | 0.0283168 m³ |
| Liters | 28.3168 L |
| US gallons | 7.48052 gal |
Liquid capacity assumes the geometric volume is fully usable. Real tanks may have walls, freeboard, internal components or an operating fill limit.
Measurement checklist
- Choose inside or outside dimensions based on the purpose.
- Use the same unit for all dimensions entered.
- Measure diameter through the center of a circle.
- Use radius only in the formula; the calculator converts diameter automatically.
- Divide irregular objects into simple shapes and add their volumes.
- Apply allowance after calculating net volume.
- Do not confuse square feet with cubic feet.
Frequently asked questions
How do I calculate cubic feet from inches?
Multiply length, width and height in inches, then divide cubic inches by 1,728. The calculator performs this conversion automatically.
How many cubic feet are in a cubic yard?
There are exactly 27 cubic feet in one cubic yard.
Can cubic feet measure liquids?
Yes. One cubic foot is about 7.48052 US gallons or 28.3168 liters.
Should I use inside or outside dimensions?
Use inside dimensions for capacity and outside dimensions for shipping space, clearance or occupied volume.
How do I calculate an irregular shape?
Break it into boxes, cylinders or other measurable sections, calculate each volume and add or subtract the sections.
Common mistakes
- Multiplying dimensions expressed in different units.
- Using diameter as radius in circular formulas.
- Applying a linear conversion to a cubic measurement.
- Using external dimensions for internal capacity.
- Rounding each dimension too early.