The grid first, and the joint is charged once per gap
A 20 foot run with 6 inches of margin at each end leaves 228 inches. Twelve inch fronts with a half inch joint sit on a 12-1/2 inch pitch, and 228 inches takes 18 of them — the arithmetic is the run plus one joint divided by the pitch, because the last front does not need a joint after it. Seven feet of usable height less 6 inches top and bottom is 72 inches, which takes 5 rows. Eighteen by five is 90 openings.
The leftovers are worth reading. Across the run, 18 fronts and 17 joints use 224-1/2 of the 228 inches, leaving 3-1/2. Up the wall, 5 fronts and 4 joints use 62 of the 72, leaving 10 inches that carry nothing — not because anything was wasted, but because a sixth row needs 12-1/2 and there are only 10.
Both counts step rather than slide, and the steps are where the design decisions sit. Holding everything else at these figures, a front height of 11-1/2 gives six rows and a front height of 12 gives five, and nothing between 12 and 14-1/2 changes the count at all. A half inch joint gives 18 columns; a three quarter inch joint gives 17. So the sensitivity is not spread evenly. It sits at a handful of boundaries, and the only way to find out whether a proposed change crosses one is to run the numbers rather than reason about them.
The companion mix changes the fronts, not the capacity
This is the part that surprises people. Say 40 percent of the niches sold are companion, and a companion is two openings wide holding two urns. Ninety openings then divide into 40 single niches and 25 companion niches, because each companion consumes two openings — 40 plus 50 is 90.
| All singles | 40% companion | |
|---|---|---|
| Openings | 90 | 90 |
| Niches sold | 90 | 65 |
| Urn capacity | 90 | 90 |
| Fronts to engrave | 90 | 65 |
| Front area | 90.00 sq ft | 91.04 sq ft |
The urn capacity does not move, because two openings hold two urns whether they are behind one front or two. What moves is the piece count: 65 fronts instead of 90. That is 25 fewer pieces to cut, engrave, set and eventually re-open, and 25 fewer separate arrangements. The front area barely changes, and it goes up rather than down, because a companion front swallows the joint that used to run between two singles.
If a companion niche in your design is two openings wide but holds only one urn — a shared front over a single chamber, say — the arithmetic inverts and every companion sold costs the wall an urn. The two fields for openings and urns are separate precisely so that case can be entered.
Height is where the money is, and this page does not price it
With the bottom row 18 inches above the walk and a 12-1/2 inch pitch, the tops of the five rows land at 30, 42-1/2, 55, 67-1/2 and 80 inches. Set the top of the comfortable band at 72 and four rows of the five are fully inside it, which is 72 of the 90 openings. The fifth row is the only one that clears it, and it clears it by 8 inches.
What that is worth is not an arithmetic question. Operators differ on how much a niche at eye level is worth against one at ankle level, some price by row and some do not, and none of that generalises. The calculator reports which rows fall where and stops, because the alternative is inventing a rule that would be wrong somewhere.
What the grid does not include
Pilasters between sections, a cap and a plinth, expansion joints, a bench or a plaque set into the run, a change of front size partway along, and the openings sacrificed wherever the design does not divide evenly — every one of those takes cells out of the count. The number here is a ceiling reached by a wall with nothing in it but fronts, which no real wall is. Draw the elevation before ordering anything, and remember that niche sizes, permitted materials and every rule about what may be inscribed on a front belong to the cemetery or the operator running the columbarium.
Questions people ask
How many niches fit in a columbarium wall?
Take the usable run, add one joint, divide by the front width plus a joint, and round down; do the same up the height. A 20 foot run at 7 feet usable, with 6 inch margins, 12 inch fronts and a half inch joint, comes to 18 columns by 5 rows, which is 90 openings. Both counts step rather than slide. At these figures an 11-1/2 inch front height gives six rows and a 12 inch one gives five, while anything between 12 and 14-1/2 gives five regardless; a half inch joint gives 18 columns and a three quarter inch joint gives 17. A row is worth as many openings as there are columns, so crossing one of those boundaries is expensive and crossing none of them is free.
Does a companion niche reduce the capacity of the wall?
Only if it holds fewer urns than the openings it occupies. If a companion is two openings wide and takes two urns, the capacity is identical to an all-single wall and only the piece count changes: 90 openings become 65 fronts at a 40 percent companion mix. If the companion is two openings wide but holds one, every companion sold costs the wall an urn. The calculator takes the openings and the urns as two separate inputs so that either case can be entered honestly.
How much engraved front area does a wall carry?
Slightly more with companion fronts than without, which is the opposite of what most people guess. Ninety single 12 by 12 fronts are 90 square feet. Sixty-five fronts at a 40 percent companion mix are about 91, because each companion front absorbs the half inch joint that used to separate two singles. The saving from a companion mix is in the number of pieces handled, not in the material.
What niche size should I use?
Whatever the columbarium is built to, which is a question for the operator and the manufacturer of the niche units rather than for a calculator. Front sizes vary widely and are usually driven by the urn dimensions the operator accepts, which are themselves the operator rules. The fields are inputs so that you can enter the real ones; nothing on this page is a recommendation about size, material or what may be placed inside.
Why does the page mark rows against a height instead of pricing them?
Because the pricing is a commercial judgement that varies by operator and by market, and a page that invented a rule for it would be wrong in most places. What is objective is geometry: at a 12-1/2 inch pitch starting 18 inches above the walk, the tops of the first five rows land at 30, 42-1/2, 55, 67-1/2 and 80 inches, and you can compare that to whatever height you consider comfortable. What follows from that comparison is yours to decide.