Reorder Level Calculator

Calculate optimal reorder levels, safety stock, and reorder points to maintain inventory efficiency while minimizing stockouts and carrying costs.

Calculate Reorder Level

Demand & Lead Time

units/day
Average units consumed per day
days
Time from order placement to delivery

Service Level & Variability

90% Service Level

Standard service level for most businesses. Z-score: 1.28

95% Service Level

High service level for critical items. Z-score: 1.65

99% Service Level

Very high service level for essential items. Z-score: 2.33

Advanced Settings

units/day
Variability in daily demand (optional)
days
Variability in lead time (optional)
units
Current inventory on hand

Reorder Analysis

Reorder Level (ROP)
0
units
Safety Stock
0
units
Lead Time Demand
0
units
Max Inventory Level
0
units

Inventory Level Visualization

Reorder Level
Safety Stock
Reorder Point
Safety Stock

Calculation Details

Average Daily Demand 100 units
Lead Time 7 days
Service Level 90% (Z=1.28)
Lead Time Demand 700 units
Safety Stock Formula Z × √(Lead Time × Demand Variance)
Reorder Point Formula Lead Time Demand + Safety Stock

Inventory Management Recommendations

  • Place new order when inventory reaches the reorder level
  • Monitor lead times regularly for adjustments

Reorder Level Calculation Guide

Reorder level (or reorder point) is the inventory level at which a new order should be placed to replenish stock before it runs out. It balances inventory costs with stockout risks.

Key Formulas

  • Reorder Level = (Average Demand × Lead Time) + Safety Stock
  • Safety Stock = Z × √(Lead Time × Demand Variance)
  • Lead Time Demand = Average Demand × Lead Time
  • Max Inventory Level = Reorder Level + Order Quantity

Service Level Z-Scores

  • 90% Service Level: Z = 1.28
  • 95% Service Level: Z = 1.65
  • 99% Service Level: Z = 2.33
  • 99.9% Service Level: Z = 3.09
  • Z-score represents standard deviations from mean

Factors Affecting Reorder Level

  • Demand variability and seasonality
  • Supplier lead time reliability
  • Desired service level and stockout tolerance
  • Ordering costs and carrying costs