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How To Measure for Custom Drawers
How to Measure and Determine the Correct Drawer Size
This guide explains how to measure cabinet openings and calculate the correct drawer box size when using undermount drawer slides such as Blum TANDEM or MOVENTO.
Quick Navigation
- Drawer Width Deduction Quick Table
- 1. Measure the Cabinet Opening
- 2. Calculate Drawer Box Dimensions
- 3. Choose Undermount Slides
- 4. Important Considerations
Drawer Width Deduction Quick Table
The width of the drawer box depends primarily on the thickness of the drawer sides and the type of undermount slide being used.
| Drawer Construction | Typical Side Thickness | Width Deduction from Opening |
|---|---|---|
| Solid Wood Drawer | 5/8" | Subtract 3/8" (up to 13/32") |
| Solid Wood Drawer | 1/2" | Subtract 5/8" (up to 21/32") |
| 11-ply Birch Drawer | 15mm (0.591") | Subtract 7/16" (up to 15/32") |
| 9-ply Birch Drawer | Approx. 0.485" | Subtract 21/32" (up to 11/16") |
Example: If the cabinet opening is 15 3/4" wide and you are using 5/8" drawer sides:
Drawer width = 15 3/4" − 3/8" = 15 3/8"
1. Measure the Cabinet Opening
Accurate measurements are critical to ensure the drawer fits properly in the cabinet.
- Width: Measure the inside width of the cabinet opening where the drawer slides will mount. Measure in multiple places and use the smallest dimension.
- Height: Measure the inside height from the bottom to the top of the opening.
- Depth: Measure the inside depth from the front edge of the cabinet to the inside of the back panel. Watch for nailers, stretchers, plumbing, or electrical obstructions.
2. Calculate Drawer Box Dimensions
Once the cabinet opening is measured, determine the appropriate drawer box dimensions based on drawer material thickness and slide type.
For most undermount slides such as Blum TANDEM or MOVENTO, the critical dimension is the distance between the inside cabinet wall and the inside of the drawer side. This measurement is typically 21mm.
The deduction from the cabinet opening depends on drawer side thickness. Refer to the quick table above for common deductions.
If the drawer is slightly narrower than recommended, it will still function but side-to-side adjustment may be reduced. If the drawer is too wide, the drawer sides may rub the slide hardware.
When using 5/8" drawer sides, it is generally safer to round the drawer width slightly smaller rather than larger.
Height Calculation
To allow for proper clearance and slide adjustment, subtract approximately 1" from the cabinet opening height.
This clearance allows space for:
- 5/8" below the drawer for the slide hardware
- 1/4" clearance above the drawer
- 1/8" adjustment range in the slides
As a general guideline, try to leave at least 7/8" clearance per drawer.
Example: If the cabinet opening height is 5 1/4":
Drawer height = 5 1/4" − 1" = 4 1/4"
Western Dovetail standard drawer heights increase in increments of one inch plus 1/4", starting at 2 1/4" (2 1/4", 3 1/4", 4 1/4", etc.). Custom heights are available if required.
Depth Calculation
The depth of the drawer box should match the slide length.
Blum recommends selecting slides that are approximately 3" shorter than the overall cabinet depth.
Example:
- Cabinet depth: 24"
- Recommended slide length: 21"
- Drawer depth for 1/2" drawers: 21"
- Drawer depth for 5/8" drawers: 21 1/16"
The inside cabinet depth should be at least 3/4" deeper than the slide length to allow proper installation.
3. Choose Undermount Slides
Proper slide selection ensures smooth operation and durability.
- Blum TANDEM slide lengths: 9", 12", 15", 18", 21"
- Blum MOVENTO slide lengths: 12", 15", 18", 21"
- Heavy-duty MOVENTO slides: 18", 21", 24", 27", 30"
Always match the drawer box depth to the slide length.
4. Important Considerations
Notching for Undermount Slides
- Blum TANDEM requires a minimum notch width of 1 3/8".
- Blum MOVENTO requires a minimum notch width of 2".
- If using another brand of slide, verify the required notch size.
Clearance Behind Drawer
- When using rear mounting brackets, allow 1" to 2" behind the drawer.
- Less than 1" is too tight and more than 2" may cause alignment problems.
Material Thickness
The thickness of the drawer sides (1/2" or 5/8") directly affects the drawer width calculation.
Full Inset vs Overlay
- Full Inset: Requires precise sizing and slide adjustment and may require depth adjustable locking devices.
- Overlay: Allows slightly more flexibility in drawer slide depth position since the front will stop at the cabinet face.
Obstacles Inside the Cabinet
- Watch for nailers, stretchers, plumbing, or wiring.
- If necessary, consider a U-shape drawer to clear obstructions.
By following these guidelines you can ensure that your drawers fit properly, operate smoothly, and maximize storage efficiency.
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