Practical tools for measured work
Drawer-Slide Clearance Calculator
Size a drawer box from cabinet opening dimensions and editable side, top, bottom and rear slide clearances.
Selecting a type loads editable starting assumptions
Use the hardware maker's specified value
Added to nominal slide length
How it works
The calculator subtracts the independently editable left and right allowances from the finished opening width. It subtracts the top and bottom allowances from opening height, and checks cabinet depth against nominal slide length plus the rear installation allowance.
Box width = opening width - left clearance - right clearanceMaximum box height = opening height - top clearance - bottom clearanceRequired cabinet depth = slide length + rear clearance
The presets are convenient starting points only. Choosing side mount assumes 12.7 mm per side; the undermount preset starts at a 42 mm total width deduction. Exact drawer dimensions differ by slide series.
Worked example: a 450 mm finished opening with 12.7 mm side clearances produces a 424.6 mm box width. Confirm that deduction against the exact slide model before cutting the drawer front, sides or bottom.
Limitations
Do not cut parts from a generic preset without checking the manufacturer's drilling diagram. Undermount systems in particular may specify drawer-side thickness, bottom recess, notch, and locking-device dimensions that this envelope calculator does not model. Center slides also vary in required bottom groove or mounting-block geometry.
The calculated box depth equals nominal slide length. Some hardware permits or requires a different box depth, and face frames may need rear sockets or blocking.
Frequently asked questions
Why are left and right clearances separate?
They are normally equal, but separate entries make asymmetric installations, spacers, and out-of-square openings explicit instead of hiding them in one total.
Is 42 mm always correct for undermount slides?
No. It is a common starting assumption for some systems, not an industry-wide rule. Enter the deduction specified for your exact slide and drawer-side thickness.
What does a negative depth margin mean?
The nominal slide plus rear allowance is deeper than the usable cabinet interior. Choose a shorter slide or confirm whether the hardware permits a smaller rear allowance.
Related tools
Drawer Box Calculator
Size a drawer box from the cabinet opening and slide length, then send the parts to a cut optimizer.
Cabinet Door Calculator
Calculate stile, rail and panel sizes for a rail-and-stile cabinet door, then send parts to a cut optimizer.
Plywood Cut Calculator
Nest an arbitrary parts list onto sheets to minimize waste, with a visual cutting layout you can print.
Linear Cut List Optimizer
Optimize cutting a list of lengths from stock bars/boards, minimizing offcuts and stock used.