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Farm size calculations
v50.13 · v0.47.05 This article is about the current version of DF.Note that some content may still need to be updated. |
Dwarves require approximately 8 units of food and 15 units of drink each year. Farming can produce enough crops to satisfy part or all of these requirements. However, be aware that the more and larger your farms are, the more labor time must be accorded to their maintenance.
The math
Your dwarves can plant 1 seed per tile on each farm plot, and depending on the skill of the grower, whether the farm plot was fertilized, and random chance, each planted tile will yield a stack of anywhere from 0 to 9 crops, depending on farmer skill and fertilization. Legendary farmers can consistently produce either 4 or 5 (average of about 4.7) without fertilizer, while they will produce 8 or 9 with fertilizer.
Brewing always quintuples stack sizes; for example, a stack of cave wheat [5] is brewed into a barrel of Dwarven beer [25] at a still. Processing quarry bush plants into quarry bush leaves at a farmer's workshop also quintuples stack size, as does processing sweet pods into Dwarven syrup. (Milling does not increase stack size.) These larger stacks are generally not usable directly as food, but can be cooked into prepared meals. Cave wheat, sweet pods and quarry bushes grow 40% slower than other crops, (although, except for cave wheat, are the ones that produce 5 times as much food,) and as long as the mature plants are harvested promptly, it is not hard to grow multiple crops of either plant each season from the same plot.
| Plant Name | Active Seasons | Days Per Harvest | Harvests Per Tile Per Season | Harvests Per Tile Per Year | Average Plants Harvested Per Tile Per Year | Average Processed Processed Food/Drink Per Tile Per Year |
|---|---|---|---|---|---|---|
| Plump helmet | 4 | 25 | 3 | 12 | 60 | 300 |
| Pig tail | 2 | 25 | 3 | 6 | 30 | 150 |
| Cave wheat | 2 | 42 | 2 | 4 | 20 | 100 |
| Sweet pod | 2 | 42 | 2 | 4 | 20 | 100 |
| Quarry bush | 3 | 42 | 2 | 6 | 30 | 150 |
| Prickle berry | 4 | 25 | 3 | 12 | 60 | 300 |
| Wild strawberry | 4 | 25 | 3 | 12 | 60 | 300 |
| Longland grass | 4 | 25 | 3 | 12 | 60 | 300 |
| Rat weed | 4 | 25 | 3 | 12 | 60 | 300 |
| Fisher berry | 4 | 25 | 3 | 12 | 60 | 300 |
| Rope reed | 4 | 25 | 3 | 12 | 60 | 300 |
| Sliver barb | 4 | 25 | 3 | 12 | 60 | 300 |
| Sun berry | 4 | 25 | 3 | 12 | 60 | 300 |
| Whip vine | 4 | 25 | 3 | 12 | 60 | 300 |
All garden crops take 25 days to reach maturity, and have identical stats to all other above-ground crops, aside from whether it is brewable, millable, or other features.
This calculation assumes all your planters have Legendary skill, and that there are enough of them to avoid any significant labor shortages at planting times.
The general limitation, then, is not the size of the farm, but the skill of the growers, as well as other labor issues: The availability of seeds, (including ensuring prompt brewing or threshing to regain seeds from crops,) ensuring no labor shortage for planting or harvesting, keeping stockpiles close to the farm for minimal travel time, availability of bags and barrels for threshing and brewing, and that crops are properly stored (in more barrels) away from vermin.
Although fertilization hypothetically doubles yields, in practice, it is almost always better to just have twice as much farm than to have to constantly designate more trees to chop, and spend another dwarf labor to burn the logs into ash and another to turn ash into potash. Since the size of even a fully-fledged fortress's farmland is generally trivial compared to the overall fortress, the only meaningful measurement of efficiency is amount of time spent in dwarf labor per unit of food. Since fertilization takes more than three times as many labors per tile to produce less than twice as much food, it is never particularly worthwhile to fertilize crops unless you are low on seeds for a given plant, and want to turn one seed into twice as many as you would get normally.
A beginning fortress has 7 dwarves, each of which consumes 8 units of food and 15 drink per dwarf per year, or 56 food and 105 drink for the whole fortress for the year. The starting group can theoretically be supported by a single farm tile, but in practice a larger farm will be necessary since a young fortress is unable to use farm tiles to their fullest potential. (Using brewed plump helmets half the year and processed quarry bushes the other half of the year.)
Taking up a "Plump helmets half the year, quarry bushes the other half" strategy with only legendary farmers, you can hypothetically produce up to 150 dwarven wine and 100 quarry bush leaves per year per tile, which is enough for 10 dwarves per tile. A whole 200-dwarf fortress can be kept fed and drunk on just 20 tiles, or a mere single 4x5 farm plot, which is small enough that a single farmer can easily work all the tiles.
Keep in mind, however, that a single farmer will likely not be able to immediately replant all seeds, (especially on the turning of Spring, and the need to replant all plots at once,) and occasionally goes on break and eats, him/herself, probably leading to getting one less harvest per year than expected on several tiles.
Also, remember dwarves require booze variety to avoid bad thoughts and desire food variety to create good thoughts. Even using less-efficient crops, like eating a (non-brewed) fisher berry is capable of feeding 7.5 dwarves per tile, and keeping 20 dwarves drunk per tile. That amounts to 10 tiles for drink and about 28 for food, or 38 total tiles even without booze-cooking or threshing for a full 200-dwarf fortress. Again, however, your farmers will not always be able to get maximum yields, but even so, about 50 tiles of farmland will provide all the food your fortress will ever need, even if divided between disparate types of less-efficient crops, and that is still within the range of what a single farmer can farm.
Additionally, if your dwarves are going to grow textiles (and dyes) for clothing they will need more farmland.
At bare minimum, each dwarf needs 4 types of clothing (torso, head, legs, and feet), taking 4 units of cloth per 3 years to prevent unhappy thoughts. Dye does nothing for happiness and is useless unless making a trade good for value. This totals up to extremely little cloth necessary to keep a fortress running - 268 cloth per year is only about 4 tiles of dedicated rope reed farm, or 8 tiles of dedicated pig tail farm for even a 200-dwarf fortress. (Just don't brew your cloth.) Additional tiles will probably be necessary for cloth to create more bags and possibly rope.
Approaches
Some fortresses begin with a single large farm (5x5) with plump helmets. However, if you embark with crops and brew them immediately, it is better to start with a few smaller farms (3x3 or 1x5 are common) with a wider variety of crops. Given the small number of dwarves, only a few tiles (about 10 total) are needed for a beginning fortresses, although you can plow a plot and leave it fallow until you have more dwarfpower to spare your farmer to dedicated farming. As the growers level up, farm yields will increase, lowering the need for large plots. Smaller plots with diverse crops can be used, instead. The more tiles of farm plot you have, the more growers (and harvesters) you will need. A single legendary farmer can seed up to about 100 tiles of farmland if they never harvest themselves and the seed stockpile is only a half-dozen tiles from all farm plot tiles. Consider making the seed stockpile in the middle of a ring of farms to save travel time.
Since a tile is "aboveground" if it has EVER been the top non-open space tile, underground and aboveground farms can be placed side-by-side, and the pit you dug to make the aboveground farm can be bridged, floored, or walled over.
If you plan to fertilize, farm plots should ideally be one less than a multiple of 4 tiles -- ex. (1x3), (1x7), (3x5), (3x9), (5x7), (7x9)