How to use this calculator
- Measure the opening. Enter the finished drawer opening width and height.
- Enter cabinet depth. Use the usable inside depth from the front reference to the back obstruction.
- Set clearances. Enter side, top, bottom, front and back allowances from slide data or shop standards.
- Enter material details. Set drawer-side thickness, bottom inset and bottom panel thickness.
- Review box parts. Use the outside box size plus side, front/back and bottom panel dimensions as a starting cut list.
How it works
Drawer box sizing starts with the finished cabinet opening. The box width subtracts the side clearance on both sides: box width = opening width - 2 x side clearance
Box height subtracts top and bottom clearance, while box depth subtracts the front setback and rear clearance from the usable cabinet depth: box depth = cabinet depth - front setback - back clearance
The part dimensions assume full-depth sides and front/back panels between those sides. After sizing the drawer box, use the cabinet face frame opening calculator when the clear opening still needs to be laid out, the cut list calculator for repeated stock lengths, dovetail spacing calculator for joinery layout, or cabinet door size calculator for adjacent door openings.
Worked example
Verified against the live calculator
A 21 in wide, 5 in tall opening with
1/2 in side clearance on each side gives a
20 in drawer box width. With 1/4 in top
clearance and 1/2 in bottom clearance, box height is
4.25 in. A 22 in cabinet depth with
1/4 in front setback and 3/4 in rear clearance
gives a 21 in box depth.
Frequently asked questions
How do I calculate drawer box width?
Start with the finished opening width and subtract the side clearance on both sides. For common side-mount slides, 1/2 in per side is often used, but the exact slide manufacturer controls the final clearance.
How do I calculate drawer box depth?
Subtract the front setback and back clearance from the cabinet inside depth. The result is the outside drawer box depth before hardware-specific slide-length choices.
Does this work for undermount drawer slides?
It can screen dimensions if you enter the clearances from the undermount slide instructions, but undermount slides often have brand-specific notch, clip, setback and drawer-side rules that are not solved here.
Are the front and back panel dimensions a complete cut list?
They are a first-pass box part list for construction where full-depth sides capture the front and back between them. Dovetails, rabbets, lock joints and groove details may change actual part lengths.
Method & assumptions
- Opening width and height are finished measured dimensions, not nominal cabinet dimensions.
- Side-mount slide guidance assumes the entered side clearance is the required clearance per side.
- Undermount slides, locking clips, notches, rear brackets and drawer-front setbacks are manufacturer-specific and must be checked separately.
- Front/back panels are assumed to fit between full-depth side panels. Joinery choices can change actual cut lengths.
- Bottom panel size is a simple inset screen; grooves, rabbets, captured bottoms and applied bottoms need shop-specific allowance.