From Hearts of Iron 4 Wiki
Jump to: navigation, search

Production refers to the manufacturing of Equipment.png equipment such as tanks, guns, planes and ships used by the military to conduct a country's war. The construction of buildings in states and provinces, including both military installations and economic development, is known as construction.


There are three types of factories:

  • Civilian factory Civilian factories: Construction (including repair), trade, and consumer goods.
  • Military factory Military factories: Infantry equipment, transport, artillery, armor, and aircraft. These have a base output of Production Cost.png 5. This value is then multiplied by Production efficiency.png Production Efficiency.
    Thus, the production formula is : \text{Production} = (\text{Base Output} \cdot \text{Output Modifier}) \cdot \text{Production Efficiency}
    For example, at 50% Production efficiency.png Production Efficiency with a 10% Modifier on Factory Output, the production would be ({5} \cdot {1.10}) \cdot {0.50} = {2.75}
  • Naval dockyard Naval Dockyards: Ships, Submarines and Convoys. Have a base output of Production cost (naval).png 2.5, but always have a production efficiency of 100%. Output do effect.

The main output modifiers for military factories and naval dockyards are Concentrated or Dispersed industry technology, while civilian factories are mainly affected by Construction industry technology and the economy law.

Production lines[edit]

See also: Construction
for Production by Civilian Factories

Production of Military and Naval Factories is organized into production lines, each of which produces a single type of equipment at a time. Up to 15 factories may be assigned to a single production line, but a country can operate lines producing the same item.

Production line legend sketch.png

Production efficiency.png Production Efficiency[edit]

Each Production Line has its own efficiency level which determines how good it is at producing its current Equipment.png equipment. The higher the efficiency, the faster the Production Line produces equipment, up to a maximum value. Running the same Production Line continuously increases its efficiency.

Production efficiency is always at least 10% and increases by a base efficiency gain of +0.25% per day up to a production efficiency cap, which starts at a base level of 50% in 1936. Both the daily gain and the cap can be increased by industry technology research and national focuses.

Production efficiency is tracked separately for each factory. Adding one or more new factories to an existing production line reduces production efficiency of the added factories. It is important to know that the factories already in the line do not lose efficiency - what they are making has not changed. Only the new factory has minimum efficiency. Also, switching a production line to a related type of equipment cancels production of the current unit and the time spent on it, and reduces its efficiency depending on how drastic the change you get to keep a % of what you have accordingly:

  • 90%: Different variant of the same model (e.g. Panzer III Ausf. F -> Panzer III Ausf. G [variants of the German medium tank 1]) 80%*0,9=72%
  • 30%: The direct upgrade of the equipment of the same type (e.g. Panzer III -> Panzer IV [German medium tank 1 to medium tank 2]) 80%*0,3=24%
  • 70%: Different model of the same chassis or airframe (e.g. Panzer III -> StuG III [German medium tank 1 to medium tank destroyer 1])80%*0,7=56%
  • 0-10%?: Different unit of the same archetype (e.g. Panzer IV -> Tiger[German medium tank 2 to heavy tank 2])

Efficiency drops to the minimum of 10% for any other changes (e.g. Infantry Equipment 1 to Towed Artillery 1).

These effects can be reduced by researching Dispersed Industry I to IV. Except for changing of variant which is always a loss of 10%.

Ships, submarines and convoys are produced in dockyards, which do not have production efficiency but still is effected by output tech. Instead, every dockyard produces a flat Production cost (naval).png 2.5 per day +output boost. Although all time and resources spent on an incomplete ship is lost if the line changes to another ship, the dockyard is at 100% efficiency as it starts the new ship design.


Each nation can use a percentage of the resources on its territory for military production. This percentage depends on the trade law, with Closed Economy.pngClosed Economy giving 100%. The total amount of resources is increased by researching Resource gain efficiency (under the tab 'industry'); each level of Resource gain efficiency increases the total of resources available for production and trade by 10%.

Resources cannot be stockpiled — they flow directly to production with any excess resources being effectively wasted.

Different kinds of equipment require different resources to produce. Lacking sufficient resources will apply an increasing efficiency penalty up to -100% to the lowest priority production lines. The penalty increases by -5% per missing unit of resource per type and the highest applicable penalty is applied to individual factories. For example, when having 2 units of steel and 0 units of aluminum available and adding a new production line for Support Equipment (needs 2 steel, 1 aluminum) with 11 factories, the first factory receives a penalty of -5% because it misses one unit of aluminum. The second factory receives -10% penalty because it both misses two units of steel and the second unit of aluminum. For each of the remaining factories the penalty increases by -10% because they need two additional steel, the last one getting a -100% penalty. The production line shows the average penalty across all factories, -50%. This penalty stacks multiplicatively with other modifiers.

There are six strategic resources.

Icon Resource Equipment
Oil.png Oil Planes, except Jet Engined
Tanks and Trucks
Rubber.png Rubber Planes
Aluminum.png Aluminum Planes
Support Equipment
Steel.png Steel Infantry Weapons and Support Equipment
Artillery, Anti-Air and Anti-Tank
Tungsten.png Tungsten Artillery and Anti-Tank
Medium Tanks
Jet planes
Chromium.png Chromium Heavy, Super-Heavy and Modern Tanks
Large ships (Carrier, Battleship and Battlecruiser)


Land divisions and air wings are not produced as atomic units. Instead, factories produce individual tanks, airplanes, and so forth. This equipment is then sent to fill out the country's land divisions and air wings. Unlike resources, equipment can be stockpiled. These stockpile can be viewed under the Logistics Tab.

Equipment Supplies
Anti-Air Anti-airAnti-air
Anti-Tank Anti-tankAnti-tank
Artillery ArtilleryArtillery
Infantry Equipment
Light Tank Light tankLight tank
Mechanized MechanizedMechanized
Medium Tank Medium tankMedium tank
Support Equipment

External links[edit]

Spreadsheet: [Hearts of Iron IV Resource Distribution by Country]