The count comes off the surface
Two divisions and a multiplication decide the whole run. Along the log, the number of holes in a row is the drillable length divided by the spacing, plus one for the hole at the start. Around the log, the number of rows is the circumference divided by the row spacing, rounded down, because the rows wrap into a closed ring and there is no leftover end to squeeze one more into.
holes per log = rows around × holes along each row
A 5 inch log is 15.7 inches around. At 2 inch row spacing that is 7 rows. A 3.5 foot bolt with 2 inches kept clear at each end has 38 inches to lay out, and at 6 inch spacing that is 7 holes to a row. Seven rows of seven is 49 holes in a log you can carry with one hand, if the rows are lined up in a straight grid. Offset the alternate rows and the count drops to 46, for the reason in the next section.
Because the count follows circumference, it scales with diameter and not with diameter squared. Weight does scale with diameter squared. An 8 inch log takes about twice the holes of a 4 inch log and weighs about four times as much, which is the entire practical argument about what size to cut, expressed in arithmetic rather than opinion.
The diamond offset, and what it actually changes
Offsetting alternate rows by half the spacing spreads the holes more evenly over the surface than a straight grid does. What it also does, and what nobody mentions, is shift where those rows start. An offset row begins half a spacing further from the end, so it sometimes fits one hole fewer than a row on the line. On the 38 inch layout above at 6 inch spacing, the rows on the line take 7 holes and the offset rows take 6, because an offset row starts 5 inches from the end and runs out of log before a seventh will fit. Seven rows on a 5 inch log is four on the line and three offset, which is 28 plus 18, or 46 holes rather than 49. The calculator counts the two kinds of row separately for that reason.
There is one more wrinkle when the row count is odd. Rows wrap around a closed circle, so the last offset row lands next to the first row on the line, and at that seam the two sit half a spacing apart instead of a full one. It does not change the count and it is not worth losing sleep over, but it is visible when you mark the log out and it surprises people.
Wax, and the number worth weighing
Wax per hole is a small number multiplied by a large one. At a gram and a half per hole, a run of 25 logs at 49 holes each is about 1,225 holes and roughly four pounds of wax. Get the per-hole figure wrong by half a gram and the run is out by a pound.
The only reliable way to get it is to weigh a block, seal fifty holes and weigh again. It depends on the dauber, the temperature and how heavy your hand is, and the range between two people doing the same job is wide. Sealing the cut ends as well is a separate decision and a separate quantity, and it is driven by area rather than by hole count — two circular faces per log, at whatever coverage rate your wax gives at the thickness you brush it on.
| Log diameter | Circumference | Rows at 2 in | Straight grid, 7 per row |
|---|---|---|---|
| 4 in | 12.6 in | 6 | 42 |
| 5 in | 15.7 in | 7 | 49 |
| 6 in | 18.8 in | 9 | 63 |
| 8 in | 25.1 in | 12 | 84 |
Stacking, and what it takes up
Round logs stacked by hand do not fill the space they occupy. Somewhere near seventy per cent wood is a reasonable working figure for straight bolts stacked carefully, and it falls quickly if the logs are crooked or the ends are ragged. The calculator turns the solid volume into a stacked volume at whatever fraction you give it, then into a rick of the height you name.
If you also handle firewood, the firewood and cord calculator does the same packing arithmetic against the 128 cubic foot cord, and the tree and log volume calculator works out what is in a standing stem before it is bucked. Neither of them counts holes.
What this page has no view on
It says nothing about which wood, which species, when to cut, when to inoculate, how to store a stack or whether anything worked. Those come from your own method or a cultivation reference. The hazards are worth naming without instruction attached: sawing and drilling are what they are, molten wax burns, and spores in quantity are a respiratory sensitiser that growers do react to over years. The yield calculator handles what comes off, and the substrate batch calculator covers the bagged side of the same craft.
Questions people ask
How many holes does a log take?
That is set by your own spacing, not by a universal number. The arithmetic is the drillable length divided by the spacing along the row plus one, multiplied by the circumference divided by the row spacing rounded down. A 5 inch log 3.5 feet long, at 6 inch and 2 inch spacings with 2 inches clear at each end, works out at 49 holes. Change either spacing and the answer moves a long way.
Does a bigger log need proportionally more spawn?
It needs more, but not in proportion to its weight. Hole count follows the circumference, so it scales with the diameter. Weight scales with the diameter squared. Doubling the diameter roughly doubles the holes and roughly quadruples what you have to lift, which is why very large bolts are hard work for the spawn they take.
How much wax will I get through?
Weigh it rather than estimating. Seal fifty holes from a block of known weight and weigh the block again. A gram and a half per hole over a thousand holes is a little over three pounds, and the spread between two people doing the same job is wide enough that a per-hole figure from someone else is not much use.
Why round the row count down instead of up?
Because the rows go round a closed circle. With a 15.7 inch circumference and 2 inch row spacing, seven rows leaves 1.7 inches at the seam — not enough for an eighth row at full spacing. Rounding up would put two rows closer together than your spacing allows, everywhere on every log.
Does the page tell me what wood or what species to use?
None at all, deliberately. The numbers that decide a growing process — the formula, the supplement rate, the spawn rate, any heat treatment, the colonisation time, the room conditions — are inputs you supply from your own tested process or a cultivation reference. This page multiplies and divides them. It cannot tell you whether a batch is clean, whether a process worked, or whether anything is safe to eat, and it does not try.