Drawer Slide Size Chart: Length, Clearance and Real Load Ratings
Measure the clear interior depth behind the cabinet face, then buy the longest even-inch slide that fits inside it. Side-mount ball bearing slides need exactly 1/2 in of clearance per side; undermount runners deduct by brand, commonly 42 mm total. Every published load rating is measured at partial extension, so derate roughly 25 percent for full extension and another 25 percent above 30 in of box width.
Measure from the inside face of the cabinet back to the back face of the front rail or face frame. That clear dimension is your ceiling. Buy the longest slide that fits under it, which in practice means the next even inch down.
A standard 24 in deep base cabinet with a 3/4 in back gives about 22 1/2 in of clear depth, so a 22 in slide fits. Metric undermount runners in that cabinet are usually 533 mm or 550 mm.
Then get the width right, because that is where projects actually go wrong. A full-extension side-mount ball bearing slide takes exactly 1/2 in per side, so your drawer box is the opening width minus 1 in, and there is no tolerance in that number. Undermount runners deduct differently by brand: Blum's Tandem system takes 42 mm off the cabinet interior width to give the box outside width, and other systems land between 3/8 in and 5/8 in total. Check the fitting instruction before you cut box parts, not after.
Measure the cabinet, never the old drawer
The old drawer tells you what somebody else did, not what fits. Take three measurements and write them on the cabinet in pencil.
Clear depth: inside face of the back to the back of the face frame or front edge. If there is a stretcher, a back rail or a plumbing chase, that is your real depth and it is often 2 in shorter than the carcass suggests.
Opening width: measure at the front, the middle and the back of the cabinet interior. Frameless carcasses bow. If the three readings differ by more than about 1/32 in, straighten the sides with a stretcher before you fit anything, because a ball bearing slide will bind on 1/16 in of bow and an undermount will simply refuse to latch.
Opening height: face frame opening on a framed cabinet, interior height between shelves or rails on a frameless one.
Cabinet depth to slide length
Cabinet exterior depth Clear interior depth (3/4 in back) Side-mount slide length Metric undermount Drawer box length to cut Notes 12 in 10 1/2 in 10 in 250 mm 10 in / 250 mm Vanity and desk pedestals 14 in 12 1/2 in 12 in 300 mm 12 in / 300 mm Shallow tool drawers, filing under a bench 16 in 14 1/2 in 14 in 350 mm 14 in / 350 mm Common in bathroom and laundry runs 18 in 16 1/2 in 16 in 400 mm 16 in / 400 mm Standard wall-hung and utility cabinet 20 in 18 1/2 in 18 in 450 mm 18 in / 450 mm Older kitchens and most shop cabinets 21 in 19 1/2 in 18 in 450 mm 18 in / 450 mm Do not force a 20 in slide in here 22 in 20 1/2 in 20 in 500 mm 20 in / 500 mm Frequently found in island bases 24 in (standard base) 22 1/2 in 22 in 550 mm 22 in / 550 mm Drop to 21 in / 533 mm if there is a back rail 26 in 24 1/2 in 24 in 600 mm 24 in / 600 mm Island and pantry boxes 30 in 28 1/2 in 28 in 700 mm 28 in / 700 mm Check the slide is rated at that length before buying Cut the drawer box length to match the slide, not to fill the cabinet. Side-mount full-extension slides require the box to be the same length as the slide, and undermounts require the box length to match the runner's nominal size within about 1/16 in or the latch will not engage. Clearances, since they do not vary by depth:
Side-mount ball bearing: 1/2 in per side, so box width equals opening minus 1 in. Side-mount epoxy roller: 1/2 in per side as well, but check, because a few older Euro systems want 12.7 mm exactly and the difference matters. Undermount: 3/16 to 5/16 in per side depending on the runner body, with Blum Tandem deducting 42 mm total from cabinet interior width. Centre mount: 1/16 to 1/8 in per side, since the box is guided by a single runner and steadied by the cabinet sides.
Three mounting types, and what each one is really for
- Side-mount ball bearing. The default. Full extension, 75 to 200 lb ratings, tolerant of an out-of-square box, and it lives entirely in the 1/2 in gap either side. The visible runner is the price you pay. Best choice for shop cabinets, tool drawers and anything where load beats appearance.
- Side-mount epoxy roller. Three-quarter extension, cheap, quiet enough, and the back third of the drawer is permanently awkward to reach. Fine in a linen cupboard. Not fine in a tool cabinet.
- Undermount. Hidden below the box, soft close as standard, and it makes a drawer feel expensive in a way nothing else does. It also demands a box built square to within about 1/32 in, a 1/2 in gap under the box, and a bottom panel captured in a groove at the right height. Unforgiving of sloppy carcass work.
- Centre mount. A single runner under the box centreline. Historically correct on period face-frame furniture, low capacity, and it lets the drawer rack side to side unless the cabinet guides it. Choose it for restoration, not for capacity.
- Wood on wood. No hardware at all, waxed runners, and a kicker above to stop the drawer tipping when it comes out. Beautiful, repairable, seasonal in its behaviour, and it needs a fitted drawer rather than a box dropped into a gap.
Load ratings, rated and derated
Every published capacity is a per-pair figure from a cycle test with an evenly distributed static load in a box of a defined width, tested to the ANSI/BHMA cabinet hardware standard. Nothing in that description resembles a 32 in wide shop drawer with all the weight at the front, pulled fully out and leaned on.
The derated columns below apply a consistent shop rule rather than manufacturer data, and the rule is stated so you can argue with it: knock 25 percent off going from three-quarter to full extension, and another 25 percent for a box over 30 in wide. That is conservative on purpose.
Slide type Published rating (per pair) At 3/4 extension At full extension Full extension, box over 30 in wide What to actually plan for Epoxy roller, 3/4 extension 75 lb 60 lb Not available Not available 35 to 45 lb Ball bearing side mount, light duty 75 lb 70 lb 55 lb 40 lb 40 to 50 lb Ball bearing side mount, standard full extension 100 lb 95 lb 75 lb 55 lb 60 to 75 lb Ball bearing side mount, heavy duty 150 lb 140 lb 110 lb 80 lb 90 to 110 lb Ball bearing, over-travel 100 lb 90 lb 70 lb 50 lb 55 to 70 lb Ball bearing, extra heavy with 1/8 in raceway 200 lb 190 lb 150 lb 115 lb 120 to 150 lb Undermount, standard soft close 75 lb 72 lb 60 lb 45 lb 45 to 60 lb Undermount, heavy class (Movento, Dynapro and similar) 130 lb 125 lb 100 lb 75 lb 80 to 100 lb Centre mount, single runner 45 lb 40 lb 30 lb 20 lb 20 to 25 lb Wood on wood, waxed, with a kicker None published n/a n/a n/a 25 to 40 lb Size from the last column. If the drawer is going to hold hand planes, router bits or a stack of cast-iron accessories, weigh a representative load on a bathroom scale before you buy, because shop drawer contents are consistently heavier than people guess. Weight is only half the story. A drawer at full extension applies a bending moment to the cabinet side, and a 3/4 in plywood side screwed to a 1/4 in back will rack long before the slide gives up. On anything over about 80 lb, use a 1/2 in captured back panel or a screwed-and-glued 3/4 in one.
Screws matter more than people expect. The pan-head screws that come in the slide box are sized for the slide's own slots; substituting countersunk screws lets the runner shift under load and shows up months later as a drawer that has developed a mind of its own.
Box height, and the tax undermounts charge for being invisible
Side-mount slides sit in the vertical middle of the box side, so the box can be almost as tall as the opening. Leave 1/2 in above and 1/2 in below for the drawer front to cover the gap and for fingers to clear.
Undermounts live underneath, and they want their space. Allow a full 1/2 in (about 13 mm) of clear height beneath the box bottom for the runner body, plus the same again in the cabinet for the mounting. That is an inch of drawer height you do not get back, and in a shallow top drawer it is the difference between usable and pointless.
Undermounts also dictate the bottom panel. The box bottom has to sit in a groove positioned so the panel's underside is flush with the bottom edge of the sides, or set at the exact dimension the runner brand specifies, usually around 12.5 mm up from the bottom of the side. Get that wrong and the locking devices at the front will not reach the panel.
Box material thickness is fixed too. Most undermount systems assume 5/8 in (16 mm) sides. Building at 1/2 in leaves the locking dowels short; building at 3/4 in means the box no longer fits the width deduction.
What goes wrong, in order of how often
- Box built 1/16 in too wide. The slides bind at the back and the drawer stops half an inch short. There is no adjustment for this; the box gets narrower or the drawer stays broken.
- Cabinet sides bowed inward. Slides that ran fine on the bench seize once the carcass is screwed to the wall. Check the width in three places before mounting.
- Slide fitted level but the carcass is not. A drawer that rolls open by itself is a cabinet out of plumb, not a faulty slide.
- Front rail thicker than the plan. On a face-frame cabinet the slide has to reach the frame or sit on a mounting bracket. A 22 in slide floating 3/4 in behind a face frame loses that much travel and gives you a drawer front that will not close flush.
- Undermount box out of square. Even 1/16 in of diagonal difference stops the locking devices seating. Square the box before the glue cures, not after.
- Overloaded at full extension. See the derating table. This one fails quietly at first, as a slide that has developed a notch you can feel, and then completely.
The order to do it in
Build the carcass and check it for square and for parallel sides. Measure the three widths and the clear depth. Choose the slide from the depth table and confirm the published length against the actual clear dimension with the slide held in place.
Only then cut the drawer box parts, using the width deduction that belongs to the slide you have physically got in your hand rather than the one you intend to buy.
Fit slides to the cabinet before the box goes anywhere near them. Use a spacer or a story stick so every pair sits at the same height on both sides, and screw through the round holes only after the slot adjustment has proved the drawer runs true.
Hang the drawer fronts last, on the drawer-front adjusters if you have them, once every box is running. Fronts are the only part of the assembly with real adjustment left in it, so let them absorb the errors.