Room size is a residence time, not a capacity
The relationship that decides the whole layout is the oldest one in production planning. The number of things sitting in a process equals the rate they arrive multiplied by how long each one stays:
blocks in the room = blocks per day × days each one stays
Fifty blocks a week is 7.14 a day. Eighteen days in the colonisation room means 129 blocks are in there at any moment. Twenty-one days of fruiting on top of that means another 150, less whatever you discarded. The building holds close to 280 blocks in order to produce 50 a week, and none of that is slack — every one of them is doing something.
The consequence people find counter-intuitive is that shortening a stage frees space without changing output at all. Take two days off the fruiting stage and the fruiting room holds fourteen fewer blocks for exactly the same weekly harvest. Add a day and it needs seven more. The same arithmetic in a single-stage form is what the formwork reuse cycle calculator does for sets of concrete forms, where the forms are the shelf and the pour interval is the arrival rate.
Turnaround time occupies floor space
A shelf slot is not free the moment a block leaves it. Clearing, cleaning and whatever rest the slot gets are all time in which that slot cannot hold a block, and it takes up exactly as much floor as an occupied one. Two days of turnaround on a 21 day fruiting stage is nearly ten per cent more racking for the same output.
This is the item that gets left out of a plan drawn on paper, because an empty shelf does not look like a cost. The page counts fruiting slots as the residence time plus the turnaround, and reports the block population separately so the difference between the two is visible.
| Starts per week | 18 days colonising | 21 days fruiting | Blocks in the building |
|---|---|---|---|
| 25 | 64 | 75 | 139 |
| 50 | 129 | 150 | 279 |
| 100 | 257 | 300 | 557 |
| 200 | 514 | 600 | 1,114 |
Those are population figures before any discard and before turnaround. They scale exactly with the rate, which is the useful property of the whole model: doubling the starts doubles every room.
The two rooms do not scale together
Anything discarded before fruiting was in the colonisation room and never reaches the fruiting room. So the colonisation room is sized on every block you start and the fruiting room on the survivors. Raise the discard rate and the fruiting room shrinks while the colonisation room stays exactly where it was — which is worth knowing before reading a rack count as a single measure of scale.
Blocks per square foot is usually different in the two rooms as well, and it is a number to measure rather than estimate. Put your own blocks on your own shelf the way you actually arrange them, count them, divide by the area. A block that is fruiting needs room around it in a way that a block sitting in the dark does not.
The first cycle is not the steady state
Every number here describes a building that has been running long enough to fill up. From empty, the colonisation room fills over the first residence time and the fruiting room over the next, so nothing reaches its planned population until well over a month in on the default figures. Space that looks comfortable in week two is fully committed by week six, and that is the point at which people discover the aisle they were using for storage is the aisle.
Where the other numbers come from
The yield per block comes from the biological efficiency and yield calculator, and the block itself from the substrate batch calculator. Fresh air for the fruiting room scales with the substrate in it rather than with the floor area, and the fruiting room fresh air calculator handles that. For the racking itself, the rack capacity calculator and the shelf sag calculator deal with what a shelf will actually carry, and the pallet rack layout calculator covers aisle geometry in a larger space.
No stage length on this page comes from the page. Colonisation time, fruiting time and turnaround are yours, from your own records or a cultivation reference, and the calculator has no view on any of them.
Questions people ask
How many blocks will be in my rooms at once?
Multiply the daily start rate by the days each block stays. Fifty a week is 7.14 a day; eighteen days of colonisation puts 129 in that room, and 21 days of fruiting puts about 150 in the other. The building holds roughly 280 blocks to produce 50 a week, and that is the steady state rather than a peak.
Does shortening a stage increase output?
No, it frees space. Output is set by how many you start, not by how long they stay. Taking two days off a 21 day fruiting stage means the fruiting room holds fourteen fewer blocks for exactly the same weekly harvest. To produce more you have to start more, and then every room grows in proportion.
Why does the fruiting room need more slots than it has blocks?
Because a slot is tied up while it is empty as well as while it is full. Clearing and cleaning between blocks is time that slot cannot hold anything, and it occupies the same floor. Two days of turnaround on a 21 day stage is nearly ten per cent more racking for the same output.
Should blocks per square foot be the same in both rooms?
Usually not, which is why the page asks twice. A colonising block can sit shoulder to shoulder; a fruiting one needs room around it for the crop and for picking. Measure both by arranging your own blocks on your own shelf and dividing by the area rather than taking a figure from anywhere else.
Does this page tell me how long each stage takes?
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.