Box Volume from Dimensions

Use this page when you have dimensions in front of you and need to get to a believable net air volume without fooling yourself with outside measurements.

Tiny Version

Box size is the inside air space after the wood, driver, port, and bracing have already stolen their room.

Step Order

1. Calculate gross inside volume from the internal dimensions.
2. Convert the answer into the units you actually want to work in.
3. Subtract driver, port, and bracing displacement.
4. Confirm the final net number still matches the design target.

Core Formulas

V_gross = L x W x H
V_net = V_gross - V_driver - V_port - V_bracing

What The Picture Should Tell You

Think of the box in three layers: outside dimensions, inside dimensions, and final net air space. The final number you design around is the inside air space after the parts take their share.

Rules Of Thumb For Deductions

These are starting estimates, not exact manufacturer specs.

• 10-inch woofer - about 0.10 ft^3
• 12-inch woofer - about 0.15 ft^3
• 15-inch woofer - about 0.25 ft^3
• 18-inch woofer - about 0.35 ft^3
• 4-inch round port x 12-inch long - about 0.06 ft^3

Unit Conversion

1 ft^3 = 1728 in^3 = 28.317 L
1 L = 61.02 in^3 = 0.0353 ft^3

Common Mistakes

• Do not use outside dimensions as if they were net air volume.
• Do not forget bracing and port displacement just because the box looks big on paper.
• Do not treat the deduction examples above as exact driver specs.