Comparing Inventory Costs using Different Order Quantity Methods for Products with Irregular Demand

Abstract

This research was comparing inventory costs using different order quantity methods for products with irregular demand. The objective of this research was 1) to calculate total inventory cost using EOQ method. 2) to calculate total inventory cost using Silver Meal method. 3) to calculate total inventory cost using Wagner-Whitin method. 4) to compare inventory costs using the EOQ, Silver Meal, and Wagner-Whitin methods. This research sample group was the top 10 best-selling products, selected using a purposive sampling method. The researchers used secondary data from the stores, covering the period from January to December 2023. This included information such as order data, sales data, expense data, payroll data, and product data. This research methodology were 1) to calculate total inventory cost using EOQ method. 2) to calculate total inventory cost using Silver Meal method. 3) to calculate total inventory cost using Wagner-Whitin method. 4) to compare inventory costs. The results of the research found that 1) Total inventory cost using EOQ method was 96,073.21 THB. 2) Total inventory cost using Silver Meal method was 67,090.42 THB. 3) Total inventory cost using Wagner-Whitin method was 62,833.82 THB. 4) The Silver Meal method could reduce inventory costs by 30.17% more than the EOQ method. The Wagner-Whitin method could reduce inventory costs by 34.60% more than the EOQ method.