Types of Inventory
Inventory is typically classified into four categories: raw materials, work-in-progress (WIP), finished goods, and maintenance/repair/operations (MRO) supplies.
Raw Materials
Basic inputs that have not yet entered the production process. These are the building blocks of your products.
Examples:
• Lumber for furniture manufacturing
• Fabric for clothing production
• Steel sheets for automotive parts
• Flour for a bakery
Management tip: Track supplier lead times and maintain safety stock to prevent production delays.
Work-in-Progress (WIP)
Partially completed goods currently in the manufacturing process. They have begun transformation but are not yet ready for sale.
Examples:
• Assembled but unpainted furniture
• Cars on the assembly line
• Dough rising before baking
• Circuit boards before final assembly
Management tip: Minimize WIP to reduce carrying costs and production bottlenecks.
Finished Goods
Completed products that have passed quality control and are ready for sale to customers.
Examples:
• Packaged consumer electronics
• Bottled beverages on shelves
• Assembled and boxed furniture
• Clothing ready for retail
Management tip: Use demand forecasting to balance availability with holding costs.
MRO Supplies
Maintenance, Repair, and Operations supplies. Items used to support production but not incorporated into the final product.
Examples:
• Machine lubricants and oils
• Cleaning supplies
• Safety equipment (gloves, goggles)
• Spare parts for machinery
Management tip: Align reorder points with preventive maintenance schedules.
Industry Examples
• Industry | Raw Materials | WIP | Finished Goods
• Furniture | Lumber, fabric, hardware | Frames, upholstered pieces | Completed chairs, tables
• Electronics | Chips, wires, plastics | Assembled PCBs | Packaged devices
• Food & Beverage | Ingredients, packaging | Batter, fermenting products | Packaged food, bottles
• Retail | N/A (buy finished) | N/A | All store inventory
Track all inventory types with StockZip
StockZip helps you organize inventory by type, location, and status. Use folders and tags to categorize raw materials, WIP, finished goods, and MRO supplies all in one system.
Frequently asked questions
What are the 4 types of inventory?
The four main types are: (1) Raw Materials - unprocessed inputs, (2) Work-in-Progress (WIP) - partially completed goods, (3) Finished Goods - completed products ready for sale, and (4) MRO - maintenance, repair, and operations supplies.
What is raw materials inventory?
Raw materials are the basic inputs used to manufacture products. Examples include wood for furniture, fabric for clothing, steel for machinery. They have not yet entered the production process.
What is work-in-progress (WIP) inventory?
WIP inventory consists of partially completed products that are still in the manufacturing process. It includes raw materials that have begun transformation but are not yet finished goods.
What is finished goods inventory?
Finished goods are completed products ready for sale to customers. They have passed through all manufacturing stages and quality checks. Examples include packaged food, assembled electronics, or sewn garments.
What is MRO inventory?
MRO (Maintenance, Repair, and Operations) inventory includes supplies used to support production but not incorporated into products. Examples: tools, lubricants, cleaning supplies, safety equipment, spare parts.
Why is it important to categorize inventory types?
Different inventory types require different management strategies. Raw materials need supplier coordination, WIP needs production flow optimization, finished goods need sales forecasting, and MRO needs preventive maintenance planning.