# Reorder Point Calculator

URL: https://speedycalculator.com/calculators/other/reorder-point/
Last updated: 2026-10-25

> The reorder point calculator tells you when to reorder stock from average daily demand, supplier lead time and safety stock, so you avoid running out.

## Inputs

- Average daily demand (units)
- Standard deviation of daily demand (units)
- Lead time (days)
- Service level

## Results

- Safety stock
- Reorder point

## Formula

```
Safety stock = z × σ_demand × √lead time
Reorder point = daily demand × lead time + safety stock
```

## Explanation

Reorder points balance the cost of holding stock against the risk of stockouts.

### How to use the Reorder Point Calculator

- **Average daily demand**
- **Standard deviation of daily demand**
- **Lead time**
- **Service level**

Results update as you type, and every field accepts the units shown in its menu.

### How it works

Expected demand during the lead time is added to a safety buffer sized for the service level you want.

### Inputs explained

FieldWhat to enterAverage daily demandIn unitsStandard deviation of daily demandIn unitsLead timeIn daysService levelChoose one: 90%, 95%, 98%, 99%

### What each result means

- **Safety stock** = [Service level]×[Standard deviation of daily demand]×sqrt([Lead time])
- **Reorder point** = [Average daily demand]×[Lead time] + [Safety stock]

### Example values

How the main result changes when **Average daily demand** changes and everything else stays at the example values above:

Average daily demand (units)Reorder point (units)201753024540315503856045580595

## Worked example

Inputs — Average daily demand: 40 units; Standard deviation of daily demand: 8 units; Lead time: 7 days; Service level: 95%.

Results — Safety stock = 35 units; **Reorder point = 315 units**.

## FAQ

**What if lead time varies too?**
Add a term for lead-time variability to the safety stock formula.

**What is a service level?**
The probability of not running out during a replenishment cycle.

**What formula does the Reorder Point Calculator use?**
Safety stock = z × σ_demand × √lead time.