Lead Time Demand Calculator
Calculate Lead Time Demand step by step: average daily demand × average lead time.
In short
Formula: Lead-time demand = average daily demand × average lead time. σ = √(L × σd² + d² × σL²) when variability is entered.
What this calculator does
Calculate Lead Time Demand step by step: average daily demand × average lead time. Worked example, questions and limitations included.
Use it to turn Average daily demand, Average lead time, Std. deviation of daily demand (optional), Std. deviation of lead time (optional) into a checked result you can compare, copy, or rerun with different assumptions.
The page shows the formula, a numeric worked example, and the assumptions that affect this supply chain calculation.
Inputs and what they mean
- Average daily demand
- — number value.
- Average lead time
- — number value.
- Std. deviation of daily demand (optional)
- — number value.
- Std. deviation of lead time (optional)
- — number value.
How to use it
- Enter each value in the unit shown next to the box (use the unit converter first if your numbers are in other units).
- Check the breakdown to see every intermediate step.
- Read the limitations before relying on the result.
Formula
Silver, Pyke and Thomas; ASCM dictionary.
No service level, distribution or z is applied — this reports expected demand and its spread only.
Turn spread into safety stock with the safety stock calculator.
Lead-time demand = average daily demand × average lead time. σ = √(L × σd² + d² × σL²) when variability is entered.
Inputs used: Average daily demand, Average lead time, Std. deviation of daily demand (optional), Std. deviation of lead time (optional).
Worked example
Expected demand
- 40 × 7 = 280 units.
Reading the result
The headline figure is the main answer. Any breakdown underneath shows the parts that make it up, so you can check the working and see what changes when you adjust an input.
Limitations and assumptions
- Averages only.
- Independence assumed for the spread.
- No distribution chosen.
- Results are planning estimates built only from the figures you enter. No prices, rates, demand patterns or service levels are built in, and the results are not supplier quotes or carrier rates.
- The result depends on the values you enter for this lead time demand calculator; it does not supply missing rates, rules, prices, dates, or assumptions for you.
Common questions
Why no safety stock here?
That needs a service level, which is your decision. Use the safety stock calculator.
What if I leave the deviations blank?
You get expected demand only. Check the formula, example, and limitations on this page before using the result for a real supply chain decision.
Weekly data?
Use weekly demand and lead time in weeks. Check the formula, example, and limitations on this page before using the result for a real supply chain decision.
How do I use the Lead Time Demand Calculator?
Enter the required values for Average daily demand, Average lead time, Std. deviation of daily demand (optional), Std. deviation of lead time (optional). The calculator applies the formula on this page and shows the main result with any supporting breakdown so you can check the arithmetic.
What formula does the Lead Time Demand Calculator use?
Lead-time demand = average daily demand × average lead time. σ = √(L × σd² + d² × σL²) when variability is entered. The visible formula section above lists the calculation path and the edge cases the page handles, so the result can be checked without relying on the form alone.
Can the Lead Time Demand Calculator be used for exact decisions?
Use it as a calculation aid, not as a substitute for checking the underlying rule, contract, policy, or professional advice that applies to your situation. When a result depends on local rules, personal details, prices, or dates, enter those values yourself and confirm them before acting.
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