Calculator
Cabinet Run & Filler Calculator
Base cabinets are sold in fixed widths — 36, 33, 30, 27 inches and down to 9 — not cut to fit a wall, so a kitchen run is really a bin-packing problem: which combination of standard boxes gets closest to the usable wall length without going over. Whatever doesn't divide evenly becomes filler, a narrow strip of matching panel between the last box and the wall or the appliance, and how much filler you end up with depends on which boxes you pick, not just how long the wall is.
This calculator fills the wall from the widest standard cabinet down, the way a kitchen designer lays out a run on paper, and reports the filler that's left over along with whether that filler reads as an intentional reveal or as a mistake. A filler strip an inch wide looks like a design choice; one four inches wide usually looks like the boxes didn't fit and nobody adjusted the plan.
Calculate your quantity
Range, dishwasher or fridge opening in this run.
Walls are never square; leave yourself something to plane.
Base cabinets
3 cabinets
Filler needed
4.75 in
- Wall run
- 144 in
- Appliance gap
- 30 in
- Usable cabinet run
- 112.75 in
- Cabinet width total
- 108 in
- Filler per side
- 2.38 in
- Widest box in the run
- 36 in
- End panels
- 1 panels
- Filler comes to 2.38 in per side, inside the 3 in that reads as intentional.
Shopping summary
- • 3 base cabinets: 36 + 36 + 36 in
- • 2 filler strip(s), 2.38 in each side
- • 1 finished end panel(s)
This is an estimate — confirm structural work with a professional.
How this calculation works
The wall run is reduced to a usable length first: the appliance gap (a range, a dishwasher, a sink base opening — anything not filled by a standard box), the width of any finished end panels, and a scribe allowance for the small gap left against a wall that isn't perfectly straight all come off before any cabinet fitting starts.
What's left is filled greedily from the widest standard width down: as many 36 in boxes as fit, then as many 33s as fit in what's left, and so on down through 9 in, stopping only when nothing smaller fits. Whatever remains after the smallest standard width no longer fits is the filler, split evenly between both ends of the run rather than dumped entirely at one side.
- Filling greedily from the widest box down tends to leave the smallest possible leftover, but it is not guaranteed to be the smallest leftover mathematically possible — a different combination of box widths can occasionally beat it by an inch or two.
- Filler over roughly 3 in per side starts to look unintentional rather than designed; the calculator flags this rather than silently accepting any leftover as fine.
- A run with no appliance gap and no end panels has more usable length to fill and therefore usually less filler, but the boxes chosen still come from the same fixed list of standard widths.
- Swapping one wide box for two narrower ones changes the filler by whatever the width difference is between the two combinations — this is the lever available on-site when a filler comes out wider than wanted.
The formula
usable run = wall run − appliance gap − (end panels × panel thickness) − scribe allowance; boxes fill greedily from widest to narrowest standard width; filler = usable run − sum of chosen box widths
- usable run
- The wall length actually available for standard cabinet boxes, after the appliance gap, end panel thickness and scribe allowance are subtracted — this, not the raw wall measurement, is what gets filled.
- appliance gap
- The width reserved for anything that isn't a standard cabinet box sitting in this run — a range, a dishwasher opening, an integrated fridge bay — entered once as a single deduction from the usable run.
- scribe allowance
- A small margin held back because walls are rarely perfectly straight; without it, a cabinet cut to the exact wall measurement can bind against a bowed section of drywall and refuse to sit flush.
- filler
- What's left of the usable run after the largest combination of standard box widths that fits has been chosen. Split evenly across both ends of the run rather than concentrated at one side, unless a design reason argues for asymmetry.
- acceptable filler per side
- The threshold below which a filler strip reads as an intentional reveal rather than a leftover the layout couldn't absorb — a working design judgment, not a manufacturing tolerance.
Where these numbers come from
- 36, 33, 30, 27, 24, 21, 18, 15, 12, 9 in standard base widths
- Manufacturer-published nominal sizing — these widths are the near-universal standard line across stock and semi-custom cabinet manufacturers in North America, in 3 in increments. Custom cabinetry can be built to any width, which defeats the purpose of this page's bin-packing logic entirely.
- 3/4 in finished end panel thickness
- Trade convention — matches typical cabinet-grade plywood and MDF panel stock used for finished cabinet ends. A thicker decorative end panel would need this figure adjusted up.
- 3 in acceptable filler per side
- Working design convention rather than a manufacturer spec: filler under about 3 in per side reads as a deliberate reveal in most kitchens, while filler wider than that starts to look like an unplanned leftover. Individual designers and clients vary on where this line actually sits.
- 0.5 in default scribe allowance
- Trade convention for a wall in reasonably straight condition. Older homes with visibly wavy drywall or plaster commonly need more; a laser-checked, recently built wall can sometimes run less.
Worked examples
A 12 foot kitchen wall with a range and one finished end
| Wall run | 12 ft |
|---|---|
| Appliance gap | 30 in |
| Finished end panels | 1 |
| Scribe allowance | 0.5 in |
| Acceptable filler per side | 3 in |
| Base cabinets | 3 cabinets |
|---|---|
| Filler needed | 4.75 in |
| Wall run | 144 in |
| Appliance gap | 30 in |
| Usable cabinet run | 112.75 in |
| Cabinet width total | 108 in |
| Filler per side | 2.38 in |
| Widest box in the run | 36 in |
| End panels | 1 panels |
After the 30 in range gap, the 0.75 in end panel and the 0.5 in scribe allowance come off, 112.75 in of usable run is left, and three 36 in boxes fill 108 in of it, leaving 4.75 in of filler — 2.38 in per side once split. That's inside the 3 in per side that reads as intentional, so this filler can sit as a clean reveal rather than needing a design change.
It's worth noticing that three 36s was the greedy choice here, not the only one — 30 plus 24 plus 33 also totals 87 rather than 108 and leaves far more filler, so the greedy widest-first fill genuinely found the tightest fit available from these standard widths, not just a reasonable one.
A tight 9.5 foot run with no appliance and a strict filler tolerance
| Wall run | 9.5 ft |
|---|---|
| Appliance gap | 0 in |
| Finished end panels | 0 |
| Scribe allowance | 0.25 in |
| Acceptable filler per side | 1.5 in |
| Base cabinets | 3 cabinets |
|---|---|
| Filler needed | 5.75 in |
| Wall run | 114 in |
| Appliance gap | 0 in |
| Usable cabinet run | 113.75 in |
| Cabinet width total | 108 in |
| Filler per side | 2.88 in |
| Widest box in the run | 36 in |
| End panels | 0 panels |
With no appliance gap or end panel to deduct, this shorter wall still lands on the same three 36 in boxes as the first example — the widest-first fill takes the same path whenever three 36s fit and a fourth doesn't. But the usable run here is 113.75 in against 5.75 in of filler, and split two ways that's 2.88 in per side, over the tighter 1.5 in tolerance this kitchen was designed to.
That's the point where the plan should change rather than the filler being accepted: swapping one 36 in box for a 33 and adding the 3 in difference to the filler moves it further from the tolerance, but swapping toward a narrower combination that leaves less total leftover — or accepting one wider box against a slightly asymmetric reveal — are the two real options once filler alone can't be trimmed down.
Common mistakes
- Measuring the wall's raw length and skipping the appliance gap, end panel and scribe allowance deductions — the usable run this page fills is always shorter than the tape-measure length of the wall.
- Assuming the filler this page reports is a mistake to be eliminated rather than a normal byproduct of fixed cabinet widths — a small filler strip is standard practice, not a sign the plan is wrong.
- Concentrating all the filler at one end when the design calls for a centred or symmetric layout — this page splits filler evenly by default, but an off-centre appliance or sink can call for an intentionally asymmetric split instead.
- Choosing box widths by eye rather than letting the widest-first fill run its course, then discovering a hand-picked combination leaves more filler than the calculated one would have.
- Forgetting that a scribe allowance is not the same deduction as a finished end panel — a wall meeting cabinetry with no panel still needs the scribe gap, and a panel doesn't replace it.
Shopping summary
Order the standard-width boxes this page selects, listed left to right as chosen, along with filler stock cut to the calculated width per side — most filler is ordered as a single wide strip and ripped to size on-site rather than pre-cut to an exact dimension.
Cabinets set the height line and depth that the countertop calculator needs next — run that page once the boxes are chosen and level, since countertop overhang and edge length both depend on where the cabinet run actually ends up, not on the wall's raw dimensions. Uppers, if this run includes them, are typically ordered to match the base run's box widths rather than calculated independently.
If this kitchen also needs new flooring installed before the cabinets go in, work that out separately with the flooring calculator first — flooring under a cabinet toe kick is usually skipped to save material, which changes the area that calculator needs from the room's full square footage.
FAQ
Is the filler this page calculates always split evenly between both ends?
By default, yes — the arithmetic here treats the leftover as a single pool split two ways. In practice a kitchen with an off-centre window, sink or appliance often calls for pushing more filler to one side intentionally; treat this page's even split as the starting point for a design decision, not the only valid layout.
Why did the calculator choose three 36 in boxes instead of some other combination that also fits?
Because it fills greedily from the widest standard width down, which is how most kitchen designers lay out a run by hand and tends to minimise leftover filler, though not with a mathematical guarantee. If a narrower combination is available and preferred for another reason — resale value of matching a neighbour's layout, or box cost — it can still be priced manually against the filler this page reports.
What counts as the appliance gap if I'm not sure yet which range I'm buying?
Use 30 in as a working stand-in — it's the standard range opening width most codes and manufacturers build to — and re-run the numbers once the actual appliance is chosen, since ranges do come in 24, 30 and 36 in widths and the filler total shifts by exactly the difference.
How much filler is actually acceptable before it looks like a mistake?
There's no fixed rule, but roughly 3 in per side is a common working line: narrower than that reads as an intentional reveal strip, wider starts to look like the cabinets didn't fit the space. The threshold in this calculator is adjustable because different kitchens and different eyes draw that line in different places.
Do finished end panels always need to be included in the calculation?
Only where a cabinet run ends in the open rather than against a wall or another cabinet — an end that butts into a wall or continues into an upper run typically doesn't need a finished panel. Set the end panel count to zero for runs where both ends are enclosed.
Can I use this for an island instead of a wall run?
Yes, if you treat the island's total perimeter length as the wall run and set the appliance gap to whatever the island needs to leave open (a prep sink or a cooktop, for instance) — the same greedy-fill logic applies, though an island commonly needs finished panels on more than one side, which this page's single end-panel count doesn't fully capture without running it twice.
Where to go next
The projects this number is a step of, the guides that explain the method behind it, and the rest of its trade group.