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Calcimator

Drawer Construction Calculator

Calculate drawer box dimensions, slide sizing, cut list, and material needs from your cabinet opening measurements and joint type.

About this calculator

Sizing a drawer starts from the cabinet opening and works backward, subtracting the clearance your slide hardware actually needs. That clearance is slide-type specific: side-mount ball-bearing slides eat a full 1/2" per side (1" total off the opening width), under-mount slides need only 3/16" per side, and wooden runners need just 1/16" — so switching slide types changes the drawer box width by nearly an inch even on an identical opening. Box height is trimmed similarly (5/8" for under-mount, 1/2" for side-mount) to clear the slide mechanism above. The calculator also rounds your available depth down to the nearest standard commercial slide length (10" through 24", in 2" steps) after reserving 1" behind the box for clearance and another 1" for the slide-to-box gap, so you buy hardware that actually exists rather than a custom size.

Cut lengths for the box parts depend on joint type: rabbet joints let front and back pieces run the full box width (the rabbet hides the joint), while butt, dovetail, and box joints all shorten front/back by twice the material thickness so the sides can wrap or interlock at the corners. The bottom panel is assumed to be 1/4" plywood riding in a 1/4" dado set 1/4" up from the bottom edge. Weight capacity is a rough hardware-based estimate, not a calculated strength value — the real limiting factor is almost always the slide rating, not the wood joinery, so don't rely on it for load-bearing design decisions.

Inputs

in
in
in
in

Results

Drawer box width (in)

17

Recommended slide length (in)

20

Drawer box height (in)5.5
Drawer depth (in)21
Side piece cut length (in)21
Front/back cut length (in)16
Bottom panel width (in)16.5
Bottom panel depth (in)20.5
Total box board feet1.41
Total bottom plywood (sq ft)2.35
Interior volume (cu in)1,600
Slide weight capacity (lbs)100
Joint Overlap0.5
How to Use This Calculator
  1. Enter the Cabinet Opening Width, Opening Height, and Cabinet Depth in inches.
  2. Select Joint Type (butt, rabbet, dovetail, or box) and Slide Type (side-mount, under-mount, or wood).
  3. Enter the Side Material Thickness and Number of Drawers for scaled material totals.
  4. Review Drawer Box Width and Height, Slide Length, and all cut dimensions for parts.
  5. Check Total Box Board Feet, Total Bottom Plywood, and Slide Weight Capacity for purchasing and design validation.

How the result changes with Cabinet opening width (in)

Cabinet opening width (in)Drawer box width (in)Recommended slide length (in)
9820
141320
272620
454420

What each input means

Cabinet opening width (in)
Interior width of the cabinet opening the drawer fits into.
Cabinet opening height (in)
Height of the opening for this drawer.
Cabinet depth (in)
Internal front-to-back depth of the cabinet.
Joint
Corner joint type. Dovetail and box joints are strongest.
Slide
Slide type affects clearance. Side-mount needs 1/2 inch per side.
Side material thickness (in)
Thickness of drawer side stock. 1/2" is standard; 3/4" for heavy-duty.
Number of drawers
Number of identical drawers to calculate material totals for.

What each result means

Drawer box width (in)
Outer width of the drawer box after slide clearance.
Drawer box height (in)
Outer height of the drawer box after top clearance.
Drawer depth (in)
Front-to-back depth of the drawer box.
Recommended slide length (in)
Nearest standard slide length that fits your cabinet depth.
Side piece cut length (in)
Cut length for each drawer side.
Front/back cut length (in)
Cut length for sub-front and back pieces.
Bottom panel width (in)
Width of the 1/4" plywood bottom panel.
Bottom panel depth (in)
Depth of the 1/4" plywood bottom panel.
Total box board feet
Board feet of hardwood needed for all drawer sides, fronts, and backs.
Total bottom plywood (sq ft)
Square feet of 1/4" plywood for all drawer bottoms.
Interior volume (cu in)
Usable interior storage volume of each drawer.
Slide weight capacity (lbs)
Approximate weight capacity per pair of slides.

How this is calculated

Worked example, using the default values

  1. Identify Input Parameters
    4 parameters
    Cabinet opening width (in) = 18, Cabinet opening height (in) = 6, Cabinet depth (in) = 22, Joint = 2 = 7 input(s) provided
  2. Calculate Drawer box width
    Drawer box width = openingWidth - totalSlideClearance
    17 = 17
  3. Calculate Recommended slide length
    Recommended slide length
    20 = 20
  4. Calculate Drawer box height
    Drawer box height = openingHeight - topClearance
    5.5 = 5.5
  5. Calculate Drawer depth
    Drawer depth = cabinetDepth - 1
    21 = 21

Engine last updated . Checked against 2 independently-derived tests — how we verify calculators. Built by Paul Gunder, a software engineer, not a licensed financial, medical, or legal professional.

Frequently Asked Questions

Why does the drawer box width change so much just from switching slide type?

Each slide type reserves a different clearance per side before the calculator subtracts it from the opening width: side-mount ball-bearing slides need 1/2" per side (1" total), under-mount slides need 3/16" per side, and wooden runners need only 1/16" per side. On an 18" opening that's the difference between a roughly 17" box and a nearly 17.9" box, so the box width isn't fixed once you fix the opening — it depends on hardware choice.

Why does the recommended slide length come out shorter than my drawer depth?

The calculator first subtracts 1" from cabinet depth for rear clearance to get drawer depth, then subtracts another 1" from that for the slide-to-box gap before rounding down to the nearest standard commercial length (10" to 24" in 2" steps). That two-step reservation is why a 22" cabinet depth can recommend an 18" or 20" slide rather than a size close to 21" or 22".

Why does changing the joint type change the front and back cut length but not the sides?

Side length is always the full drawer depth regardless of joinery, but front/back length depends on how the corner is cut: a rabbet joint lets the front and back run the full box width because the rabbet itself conceals the joint, while butt, dovetail, and box joints all shorten front and back by twice the material thickness so the sides can wrap around or interlock at the corners.

Can I trust the slide weight capacity number for a heavy-duty drawer?

No — slideCapacityLbs is a rough lookup keyed only to slide type and whether the slide is 18" or longer (for example, 100 lbs for a long side-mount slide, 30 lbs flat for wood runners), not a computed value from your specific dimensions or joinery. Always check the actual hardware manufacturer's rated capacity before loading a drawer for storage.

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