Supply Chain & Operations Lab

Inventory EOQ & Reorder Point Lab

Calculate Economic Order Quantity (EOQ), Safety Stock buffers, Reorder Point (ROP), and annual carrying cost curves across retail and manufacturing inventory systems.

Inventory Model Batch Size Cost Curve EOQ & Supply Chain Theory FAQ

Supply Chain Presets

Load calibrated inventory & replenishment models.

Step 1: Demand & Carrying Cost Assumptions

Inventory Demand & Replenishment Parameters

1. Demand & Purchasing Costs

$
$
Procurement processing, freight setup & receiving.
%
Capital cost, warehouse storage, insurance & shrink.

2. Supplier Lead Time & Volatility

Calculates safety stock buffer needed to prevent stockouts during supplier transit based on normal demand distribution.
Economic Order Qty
0 Units
Reorder Point (ROP)
0 Units
Safety Stock Buffer
0 Units
Orders Per Year
0.0 / Yr
Cycle Time
0.0 Days
Total Annual Policy Cost
$0

Step 2: Order Batch Size Cost Curve

Ordering vs. Holding Cost Tradeoff

Illustrates why EOQ is mathematically optimal: smaller batches trigger excessive setup fees, while oversized batches create heavy carrying costs.

Order Batch Policy Orders / Year Annual Ordering Cost ($) Annual Holding Cost ($) Total Carrying + Ordering ($)

Supply Chain Guide

Understanding inventory optimization

Inventory management balances customer product availability against working capital financing and warehouse holding costs.

  • The EOQ Equilibrium: At the Economic Order Quantity, total annual ordering setup costs exactly equal total annual cycle holding costs.
  • Safety Stock vs. Service Level: Increasing customer fill rate from 95% to 99% increases safety stock by over 41%, requiring more tied-up cash.
  • Lead Time Uncertainty: Reducing supplier transit days cuts lead time demand and compresses safety stock requirements.

Model working capital cash drag in the Cash Conversion Cycle Simulator.

Operations Equations

Essential inventory formulas

EOQ = √ [ (2 × Demand × Setup Cost) ÷ Unit Holding Cost ]

Reorder Point (ROP) = (Daily Demand × Lead Time) + Safety Stock

Safety Stock = Z × Daily Std Dev × √(Lead Time)

Annual Ordering Cost = (Demand ÷ Batch Size) × Setup Cost

Annual Holding Cost = (Batch Size ÷ 2 + Safety Stock) × Holding Cost

Test defect prevention in the Cost of Quality Lab.

FAQ

Inventory EOQ and Reorder Point questions

What is Economic Order Quantity (EOQ) and what does it optimize?

EOQ is the ideal order batch size that minimizes total annual inventory costs by finding the exact balance point where annual order setup costs equal annual inventory holding/carrying costs.

What is the Reorder Point (ROP) and how is safety stock factored in?

Reorder Point (ROP) is the inventory level that triggers a new replenishment purchase. It equals expected demand during supplier lead time plus a safety stock buffer to protect against demand volatility.

Why do holding costs increase as order size increases?

Ordering in larger batches raises average inventory in the warehouse, increasing capital financing costs, storage footprint, insurance, handling, spoilage, and obsolescence risk.

How does Target Service Level impact safety stock?

Higher service levels (e.g. 99% vs. 90%) require higher Z-scores, demanding exponentially larger safety stock buffers and tied-up working capital to prevent stockouts during unexpected demand spikes.

Can I export inventory EOQ and ROP calculations to CSV?

Yes. You can export complete inventory parameters, order batches, safety buffers, reorder points, and cost breakdowns as a UTF-8 CSV spreadsheet with formula injection defense or print an executive purchasing brief.

Are these calculations guaranteed supplier replenishment commitments?

No. This tool provides simplified educational models for supply chain training without guaranteed supplier minimum order quantities (MOQs), freight tiered discounts, or formal procurement contracts.

Continue Exploring Operations & Retail Tools

Explore our Retail & Inventory Simulation Hub, optimize cash velocity in the Cash Conversion Cycle Simulator, simulate quality costs in the Cost of Quality Lab, or calculate staffing needs in the Staffing Capacity Lab.