Two constraints, and the one that binds is usually the vertical
Set a panel 30 by 14 with an inch and a half of margin all round and you have 27 by 11 to letter in. At a 1-1/2 inch cap height with characters averaging 60 percent of that and a quarter inch between them, each character occupies 1.15 inches of line, so 27 inches takes 23 characters. Four lines at 1-1/2 with an inch between them is 9 inches, inside the 11 available.
Now ask how big the letters could be. The longest line in a typical four-line inscription runs about 18 characters, and 18 characters across 27 inches allows a cap height of 2-3/32. Four lines across 11 inches of height allows 2 inches exactly. The height wins, and it usually does, because lines cost a full cap height plus a full gap each while characters cost a fraction of one.
| Cap height | Characters per line | Lines in 11 in | Panel capacity |
|---|---|---|---|
| 1 in | 32 | 6 | 192 |
| 1-1/4 in | 27 | 5 | 135 |
| 1-1/2 in | 23 | 4 | 92 |
| 2 in | 18 | 4 | 72 |
| 2-1/2 in | 15 | 3 | 45 |
Capacity moves in both directions at once, which is why it does not track the letter height in any simple way. Going from a 1-1/2 inch letter to a 2 inch one costs about a fifth of the panel, 92 characters down to 72, because the line count happens to hold at four across that step. Going the other way, from 2 inch letters down to 1 inch, does not double the capacity — it nearly triples it, 72 up to 192, because the characters get narrower and two more lines appear at the same time. The steps are uneven, and they are uneven in a way that only the arithmetic shows.
Character width is an average and averages lie on short lines
Nothing here is monospaced. In a normal Roman alphabet an M is close to a square, an I is a stem, and the numerals are usually cut to one width so that dates line up. A line reading 1931 - 2014 is eleven characters and takes far less room than eleven letters of a surname. The 60 percent default is a starting point for a normal Roman and it will be several percent out for anything condensed, extended or Gothic.
The practical consequence is that the count is reliable at fifteen characters and unreliable at five. On a long line the errors average out; on a short one a single wide letter moves it. Anybody who sets lettering for a living proofs it at full size on paper, tapes it to the stone, and stands back — and does that before agreeing the layout, not after.
The stencil covers the panel and the blast covers almost none of it
A four-line inscription of about 49 cut characters at a 1-1/2 inch cap, with each character actually covering a fifth of its box, blasts around 13 square inches. The stencil goes over the whole 30 by 14 face, which is 420 square inches. Roughly three percent of what gets covered gets opened.
That ratio explains two things about how the work is priced. Stencil is bought by the panel and barely moves with the length of the inscription, so a short inscription is not much cheaper in material than a long one. And blasting time on lettering is governed by the length of the cut edge rather than by the open area, which is why an intricate script at a small cap height takes longer than plain block capitals twice the size.
Line gap gives less than you think
When an inscription is a fraction too tall, the instinct is to close the line spacing. On four lines there are three gaps. Taking a quarter inch out of each recovers three quarters of an inch total, and it does it by making the block of text visibly tighter. Dropping the cap height by an eighth recovers half an inch across the four lines and nobody sees it. Neither is free, but the second is cheaper than it looks and the first is dearer.
Questions people ask
What cap height is normal for a headstone inscription?
There is no standard, and what a cemetery permits on a marker it owns the rules for is its own business. What drives the choice in practice is the panel and the wording, worked backwards: the longest line sets a maximum and the number of lines sets another, and the smaller of the two is what you get. Names on an upright die commonly land somewhere between an inch and three inches, with dates a shade smaller than names, but that is an observation about proportion rather than a rule.
How do I count characters for a line of dates?
Count every character including the spaces and the dash, because they all take room on the line. The calculator counts spaces for width and excludes them from the blasted area, which is the right way round: a space costs you line length and costs you nothing in stencil. Where the count misleads is that numerals are usually narrower than the average letter, so a date line will fit more comfortably than the arithmetic suggests.
Why does the biggest letter that fits depend on the number of lines?
Because each extra line costs a full cap height plus a full gap, while each extra character costs only a fraction of a cap height. Four lines at a 2 inch cap with a 1 inch gap need 11 inches of height. Five lines need 14. Add one line to an inscription and the letters have to shrink to pay for it, which is why the fifth line is the expensive one and why families are often asked to choose between a middle name and a legible date.
Does this work for a laser-etched or hand-cut inscription?
The layout arithmetic does, because it is only about how many boxes fit in a rectangle. The blasted area figure is specific to sandblasting through a stencil and means nothing for hand cutting or laser work. Depth, edge quality and how the inscription reads at a distance all differ between the methods in ways no dimension calculation reaches, and the choice between them belongs to the shop doing the work.
Can I use this to add a line to an existing stone?
For checking whether the space is there, yes — measure the clear panel that remains, not the original one, and set the cap height and spacing to match what is already cut rather than to what fits. Matching an existing inscription is the hard part and it is not a dimension problem: the alphabet, the cut depth, the weathering and the colour of the older lettering all have to be matched by somebody looking at the stone. That is a conversation with a monument dealer, and it is worth having before the panel is measured.