Interior Volume Formula
Interior volume accounts for the material thickness of walls and bottom to give you the actual usable space inside a box, cabinet, or drawer.
Last updated: 2026-02-27
Box Volume Calculator
Calculate interior volume for boxes, cabinets, and drawers accounting for material thickness. Get accurate capacity measurements for woodworking projects.
Interior Volume Material Thickness Unit Conversion Capacity Planning
Box Dimensions
in
in
in
Volume Results
Enter box dimensions to calculate interior volume.
Interior volume accounts for wall and bottom thickness. Always verify measurements before cutting. Remember to subtract additional clearances for drawer slides, hinges, and hardware.
How to Use This Calculator
- 1 Enter Outer Dimensions Input the outer length, width, and height of your box in inches.
- 2 Set Wall Thickness Select the wall material thickness (1/4 in, 3/8 in, 1/2 in, or 3/4 in).
- 3 Set Bottom Thickness Select the bottom panel thickness, which may differ from the walls.
- 4 Review Results Get interior dimensions, volume in cubic inches, and converted units (gallons, liters, cubic feet).
Pro Tip: For drawers, subtract an additional 1 inch from width for slide clearance (1/2 in per side). For cabinet interiors, subtract hinge hardware thickness and door overlap.
Volume = (L - 2t) * (W - 2t) * (H - b) Common Applications
Accurate interior volume calculations are essential for drawer capacity planning, cabinet interior design, storage box sizing, and shipping calculations where contents must fit inside.
| Application | Outer Size (L x W x H) | Wall | Bottom | Interior Volume |
|---|---|---|---|---|
| Jewelry Box | 8 x 6 x 4 in | 1/4 in | 1/4 in | 79.7 cu in |
| Drawer (kitchen) | 20 x 14 x 5 in | 1/2 in | 1/4 in | 455.6 cu in |
| Tool Box | 24 x 12 x 10 in | 3/4 in | 3/4 in | 2,306.3 cu in |
| Storage Chest | 36 x 18 x 18 in | 3/4 in | 3/4 in | 9,504 cu in |
| Base Cabinet | 36 x 24 x 30 in | 3/4 in | 3/4 in | 22,736 cu in |
Interior volumes are calculated values. Actual usable space may be less due to hardware, dividers, and clearances.
Material Thickness Guide
Choosing the right material thickness balances strength, weight, and interior space. Thicker walls add durability but reduce usable volume.
| Thickness | Typical Use | Material Options |
|---|---|---|
| 1/4 in (6mm) | Drawer bottoms, small box backs, cabinet backs | Plywood, hardboard, MDF |
| 3/8 in (10mm) | Small boxes, lightweight drawers | Plywood, solid wood |
| 1/2 in (13mm) | Drawers, small cabinets, general boxes | Plywood, MDF, solid wood |
| 3/4 in (19mm) | Cabinets, large boxes, structural components | Plywood, MDF, solid hardwood |
Actual thickness may vary. Baltic birch plywood is commonly available in metric thicknesses.
Design Tips
- Account for joinery — dados, rabbets, and grooves affect interior dimensions
- Drawer slides subtract 1/2 in per side from available width
- Plan for clearances — leave 1/16 to 1/8 in gaps for seasonal wood movement
- Add dividers after calculating total volume to plan compartments
- Consider lid/top thickness if the box has a closing lid
Glossary of Terms
The usable space inside a box after accounting for wall and bottom material thickness. Measured in cubic inches, then converted to gallons, liters, or cubic feet as needed.
The thickness of the side panels. Standard options: 1/4, 3/8, 1/2, 3/4 inch. Affects both interior volume and structural strength.
The thickness of the bottom panel, which may differ from wall thickness. Drawer bottoms are typically 1/4 in while cabinet bottoms are 3/4 in.
A groove cut into one piece to receive another. Used for shelves and drawer bottoms. Reduces effective interior height by the dado depth.
An L-shaped groove cut along the edge of a board. Common for box backs and bottoms. Affects interior dimensions differently than butt joints.
Frequently Asked Questions
How do I calculate interior volume for a box?
Interior Volume = (Length - 2 x wall thickness) x (Width - 2 x wall thickness) x (Height - bottom thickness). For a 12 x 8 x 6 in box with 1/2 in walls and 1/4 in bottom: (11 x 7 x 5.75 in) = 442.75 cubic inches.
Should I use thicker walls for larger boxes?
Yes. Small boxes (under 10 in) work well with 1/4 to 1/2 in walls. Medium boxes (10-24 in) need 1/2 to 3/4 in walls. Large boxes and cabinets require 3/4 in for structural integrity. Plywood is stronger than MDF for the same thickness.
How much volume do drawer slides take up?
Standard drawer slides require 1/2 in clearance per side (1 in total width reduction). Some undermount slides require 1/2 in from the bottom. Always check slide specifications before calculating final interior volume.
How do I convert cubic inches to gallons?
Divide cubic inches by 231 to get US gallons. Example: 462 cubic inches / 231 = 2.0 gallons. For liters, divide cubic inches by 61.024.
Does joinery affect interior volume?
Yes. Dados reduce interior height by their depth (typically 1/4 to 3/8 in). Rabbets at corners can slightly increase or decrease interior space depending on the joint design. Account for joinery in precision projects.