Combat units: biter and spitter stats by tier

The enemy roster

Biters are melee units that close distance and bite. Spitters hang back and lob acid projectiles. Spawners are stationary structures that produce units and absorb hits while doing so. Worms are immobile enemy turrets that appear alongside spawners in nests. The tables below list every tier of each class with the stats available in the prototype data.

Biters (melee)

Unit	Health	Movement speed (tiles/tick)	Attack range (tiles)	Attack cooldown (ticks)
small biter	15	0.2	0.5	35
medium biter	75	0.24	1	35
big biter	375	0.23	1.5	35
behemoth biter	3000	0.3	1.5	50

Spitters (ranged acid)

Unit	Health	Movement speed (tiles/tick)	Attack range (tiles)	Attack cooldown (ticks)
small spitter	10	0.185	NOT FOUND	100
medium spitter	50	0.165	NOT FOUND	100
big spitter	200	0.15	NOT FOUND	100
behemoth spitter	1500	0.15	NOT FOUND	100

Range is not present in the prototype data for any spitter tier, so those cells read NOT FOUND. The cooldown for every spitter tier is 100 ticks, nearly three times the 35-tick cooldown of small and medium biters. Spitters attack less often but from a distance; biters attack frequently but must reach their target first.

Health spans 300x while speed barely doubles

The smallest combat unit is the small spitter at 10 HP. The largest is the behemoth biter at 3000 HP. The ratio is 300 to one. Over that same span, movement speed runs from 0.15 tiles/tick (behemoth spitter) to 0.3 tiles/tick (behemoth biter), a ratio of only 2 to one.

Biter tier	Health	Health vs small biter	Movement speed	Speed vs small biter
small biter	15	1x	0.2	1x
medium biter	75	5x	0.24	1.20x
big biter	375	25x	0.23	1.15x
behemoth biter	3000	200x	0.3	1.50x

The asymmetry matters for turret selection. A gun turret fires often but each round does modest damage. Against a small biter with 15 HP, a few rounds suffice. Against a behemoth biter with 3000 HP, the same turret must land 600 rounds before the target drops. Doubling the turret's rate of fire halves the time between shots but does not change the number of hits required. Doubling per-shot damage halves the hit count directly. When enemy HP grows two orders of magnitude faster than enemy speed, the time a target spends inside turret range is roughly constant across tiers, so the binding constraint becomes how much damage each shot delivers rather than how many shots the turret can squeeze into that window.

Bigger biters speed up; bigger spitters slow down

The two unit classes follow opposite speed curves. Biters start at 0.2 tiles/tick at small tier and reach 0.3 at behemoth tier, a 1.50x increase. Spitters start at 0.185 and fall to 0.15, a 0.81x decrease.

Tier	Biter speed	Spitter speed
small	0.2	0.185
medium	0.24	0.165
big	0.23	0.15
behemoth	0.3	0.15

There is one wrinkle in the biter curve worth flagging because it looks like a data error and is not. The big biter has a movement speed of 0.23, which is slightly lower than the medium biter's 0.24. That is the value in the prototype data for game version 2.1.12; it is not a typo on this page. The behemoth biter then jumps to 0.3, the fastest of all eight units. The practical reading is that big biters are a high-HP tier that absorbs damage rather than a pure speed upgrade, while behemoth biters combine the highest health with the highest speed.

The defensive implication is that the two classes need to be handled at different distances. Biters close quickly and must be stopped at the wall or before they reach it; their short range (0.5 tile at small, 1.5 tiles at behemoth) means they are already biting by the time they are adjacent. Spitters, by contrast, are slow enough that they arrive after the biters and then hold position at a distance, firing acid on a 100-tick cycle. A wall that absorbs biter charges can be degraded over time by spitters that never need to cross it. Turret fields that can hit spitters beyond their own attack range are more valuable against late-game nests than extra layers of wall.

How many shots to kill each unit

Only three ammo items in the prototype data expose a damage_amount field: firearm magazine at 5 damage, piercing rounds magazine at 8, and railgun ammo at 10000 (Space Age). Dividing each unit's health by each ammo's damage gives the number of hits needed, before any armor, resistance or damage research modifiers are applied.

Unit	Health	Firearm mag hits	Piercing rounds hits	Railgun ammo hits
small biter	15	3	2	0.002 (1 shot overkills)
medium biter	75	15	10	0.007 (1 shot overkills)
big biter	375	75	47	0.037 (1 shot overkills)
behemoth biter	3000	600	375	0.300 (1 shot overkills)
small spitter	10	2	2	0.001 (1 shot overkills)
medium spitter	50	10	7	0.005 (1 shot overkills)
big spitter	200	40	25	0.020 (1 shot overkills)
behemoth spitter	1500	300	188	0.150 (1 shot overkills)

For the behemoth biter, the numbers are 600 firearm-magazine rounds, 375 piercing rounds, and a railgun ratio of 0.300. The railgun figure means a single round carries 3.33 times the health of a behemoth biter. Whether that overkill translates to multiple kills per shot depends on the weapon's attack behavior (for example, piercing or area damage), which is not stored in the item prototype and is therefore not quantified here.

These are paper-damage estimates. Enemy units in Factorio have resistances that reduce incoming damage, and players research damage upgrades that increase it. Neither modifier is present in the data files used by this page, so the real hit count against a behemoth biter in a live game will differ from the figures above. The table is useful for comparing the relative cost of engaging each tier with each ammo type, not for predicting an exact round count in a specific save.

The ammo damage gap

Most of the ammo items in the prototype data define an ammo_category and a stack size but do not expose a damage_amount. For those items the per-shot damage is NOT FOUND in the data and is not estimated on this page. The table below lists them so the gap is visible rather than silently skipped.

Ammo item	Ammo category	Source	Damage
uranium rounds magazine	NOT FOUND	Base game	NOT FOUND
flamethrower ammo	flamethrower	Base game	NOT FOUND
rocket	rocket	Base game	NOT FOUND
explosive rocket	rocket	Base game	NOT FOUND
atomic bomb	NOT FOUND	Base game	NOT FOUND
piercing shotgun shell	shotgun-shell	Base game	NOT FOUND
cannon shell	cannon-shell	Base game	NOT FOUND
explosive cannon shell	cannon-shell	Base game	NOT FOUND
uranium cannon shell	NOT FOUND	Base game	NOT FOUND
explosive uranium cannon shell	NOT FOUND	Base game	NOT FOUND
artillery shell	artillery-shell	Base game	NOT FOUND
shotgun shell	shotgun-shell	Base game	NOT FOUND
capture robot rocket	rocket	Space Age	NOT FOUND
tesla ammo	tesla	Space Age	NOT FOUND

This includes several late-game ammo types such as uranium rounds, rockets, cannon shells, flamethrower fuel and artillery shells. Their damage values live in nested attack-parameter structures that the data extraction did not capture, so they cannot be quoted here. The three ammo types that do expose damage should not be read as a ranking of all available ammunition; they are simply the three whose damage the data contains.

Spawners are softer than the bugs they produce

A biter spawner has 350 HP. The behemoth biter it can produce has 3000 HP, which is 8.57 times as much. A spitter spawner has the same 350 HP. Both spawners are stationary, which means clearing a nest is a simpler problem than defending against the wave it sends: the target does not close distance, does not path around walls, and can be engaged from beyond its own production radius with the right weapon platform.

Structure	Health	Ratio vs biter spawner	Source
biter spawner	350	1x	Base game
spitter spawner	350	1x	Base game
gleba spawner	500	1.43x	Space Age
gleba spawner small	100	0.286x	Space Age

The Gleba spawners from the Space Age expansion have 500 HP (standard) and 100 HP (small variant), both of which fall between the base-game spawners and the behemoth biter on the health scale. The threat they pose comes from the units they produce rather than from their own durability, which is the same principle that applies to the base-game nests.

Worms: the stationary guns of a nest

Worms are enemy turrets that appear in nests alongside spawners. They do not move and do not produce units, but they fire at approaching players, vehicles and turrets. Their health scales across the same four tiers as the mobile units, from 200 HP at small worm to 3000 HP at behemoth worm. Every tier has an attack cooldown of 4 ticks, which is considerably faster than the 35-tick biter cooldown and the 100-tick spitter cooldown.

Worm tier	Health	Attack cooldown (ticks)
small worm turret	200	4
medium worm turret	500	4
big worm turret	1500	4
behemoth worm turret	3000	4

Worms are a secondary concern on this page because the focus is mobile combat units, but their presence affects how nests are cleared. A behemoth worm's 3000 HP matches a behemoth biter's 3000 HP, and the worm fires more often while sitting still. Rushing a nest on foot without outranging the worms is more expensive than the spawner health alone suggests.

Putting the numbers together

The data points to a few practical conclusions. First, per-shot damage scales in importance as evolution progresses because health grows faster than any other stat. A weapon that works through volume of fire against small biters may not have enough time on target against a behemoth, even though the behemoth is only twice as fast. Second, biters and spitters need different countermeasures: biters are a close-range shock that walls and short-range turrets absorb, while spitters are a slower, longer-range problem that out-ranges basic gun turrets and must be engaged from beyond their acid distance. Third, the spawners themselves are the softest high-value target in a nest relative to the units they field, which is why artillery and other long-range platforms are effective for clearing: they hit the stationary structure before it can produce another wave.

None of these conclusions should be treated as build orders or exact turret counts. The missing resistance and damage-research values mean the real numbers in a save depend on its research state and the specific enemies present. What the prototype data provides is the scale of the problem: a 300-fold health range, a 2-fold speed range, and a set of attack cooldowns that vary by nearly a factor of three between unit classes. Those ratios are what make late-game combat a different problem from early-game combat rather than a larger version of the same one.

Applies when…

• All stats are read from the prototype data for game version 2.1.12. Mods that alter enemy health, speed or cooldown will change every figure on this page.
• Gleba spawners and railgun ammo require the Space Age expansion. They are marked in the relevant tables.
• Hits-to-kill figures are paper-damage estimates: unit health divided by ammo damage_amount. They do not account for enemy resistances, armor, player damage research, or any other modifier. Real hit counts will be higher.
• Attack cooldown is the interval between attacks in ticks. It is not the same as damage per second, because DPS also depends on per-shot damage and on whether every attack hits.
• Movement speed is measured in tiles per tick. The game runs at 60 ticks per second, so multiplying by 60 gives tiles per second.
• Spitter range is NOT FOUND in the prototype data; no range value is quoted for any spitter tier.
• The big biter's movement speed of 0.23 is lower than the medium biter's 0.24. This is the value in the prototype data and is presented as-is, not treated as an error.
• Ammo types without a damage_amount field are listed as NOT FOUND. Their damage is not estimated or inferred from other sources.

Related

• Starter base — early-game wall and turret placement where the first biter waves arrive
• Smelting layouts — production buildouts that fund the ammo and turret supply line
• Quality mechanics — how higher-quality equipment and ammo can shift the damage math in your favor
• Beacons and modules — the production side of fielding enough ammunition and turrets to hold a perimeter
• Science pack ratios — the research chain that gates damage upgrades and late-game turrets
• Production ratio calculator — work out how much ammo and wall material your factory needs to sustain