How to use the Speaker / Subwoofer Box Cubic Feet Calculator
- Use the finished outside dimensions and uniform wall thickness. Enter the total occupied interior volume from driver data and enclosure parts.
- Enter external dimensions, wall thickness and the total volume displaced by internal components.
- Select Calculate. Review the result and its working; if you change an input, calculate again before copying or sharing.
Speaker / Subwoofer Box formula
Subtract twice the wall thickness from each external dimension to find the inside envelope, then subtract component displacement.
Net volume = (L − 2t)(W − 2t)(H − 2t) − driver/port/bracing displacement
What the terms mean
- External length
- A measured length in the selected unit; it is converted to feet before volume is calculated.
- External width
- A measured length in the selected unit; it is converted to feet before volume is calculated.
- External height
- A measured length in the selected unit; it is converted to feet before volume is calculated.
- Wall thickness
- A measured length in the selected unit; it is converted to feet before volume is calculated.
- Driver, port and bracing displacement
- Entered in ft³.
Speaker / Subwoofer Box worked examples
Estimate net enclosure volume
An enclosure measures 24 in × 16 in × 14 in externally, with uniform 0.75 in walls. Subtract 0.15 ft³ for driver, port and bracing displacement.
- Interior dimensions = each external dimension − 2 × wall thickness
- 1.875 × 1.208333 × 1.041667 = 2.360026 ft³
- Subtract driver, port and bracing displacement
Answer: 2.210026 ft³. Cubic yards: 0.081853 yd³; Litres: 62.580968 L; Gross interior volume: 2.360026 ft³.
Measure a larger enclosure
Use external dimensions of 30 in × 18 in × 16 in, 0.75 in walls and a total internal displacement of 0.2 ft³.
- Interior dimensions = each external dimension − 2 × wall thickness
- 2.375 × 1.375 × 1.208333 = 3.945964 ft³
- Subtract driver, port and bracing displacement
Answer: 3.745964 ft³. Cubic yards: 0.138739 yd³; Litres: 106.073875 L; Gross interior volume: 3.945964 ft³.
Speaker / Subwoofer Box Cubic Feet Calculator FAQs
Should port displacement be subtracted?
Subtract the interior volume occupied by the port structure and duct where appropriate for the enclosure design. Include driver and bracing displacement too.
Does this choose a box size for my driver?
No. Compare the calculated net volume with the driver’s recommended enclosure design.
Measurement guide for Speaker / Subwoofer Box
Measure the outside enclosure and actual panel thickness. Add driver, port and bracing displacement using consistent volume units.
Assumptions and limits
Every interior dimension is reduced by twice the wall thickness. Net volume is a geometry result; acoustic response and port tuning need a design model.
Net enclosure volume only. Port tuning and target box size come from the driver design.
Check your result
Review gross interior volume before displacement. Compare net volume with the speaker specification separately; this calculation does not tune a port.