Lead Time Demand Calculator Formula
Understand the math behind the lead time demand calculator. Each variable explained with a worked example.
Formulas Used
Lead Time Demand
lead_time_demand = daily_demand * lead_time_daysWeekly Demand
weekly_demand = daily_demand * 7Variables
| Variable | Description | Default |
|---|---|---|
daily_demand | Average Daily Demand (units) | 35 |
lead_time_days | Lead Time (days) | 14 |
How It Works
How to Calculate Lead Time Demand
Formula
Lead Time Demand = Average Daily Demand x Lead Time (days)
Lead time demand is the inventory you will consume between placing an order and receiving it. If you sell 35 units per day and your supplier needs 14 days to deliver, you must have at least 490 units available when you place the order (plus safety stock). This calculation is the foundation of reorder point planning.
Worked Example
A product sells 35 units per day on average, and the supplier lead time is 14 days.
- 01Lead Time Demand = 35 x 14 = 490 units
- 02Weekly Demand = 35 x 7 = 245 units
- 03You need at least 490 units on hand when placing an order to last until delivery.
Frequently Asked Questions
What if demand fluctuates?
If demand is variable, use the average daily demand for the lead time demand calculation, then add safety stock to buffer against above-average demand days. The more volatile your demand, the more safety stock you need.
Should I account for weekends in lead time?
It depends on your operation. If you sell 7 days a week, use calendar days. If you only sell on business days, use business days for both demand and lead time. Be consistent.
Ready to run the numbers?
Open Lead Time Demand Calculator