# Spare Parts Reorder Point and Safety Stock Calculator for SAP PM

> Source: https://netray.co/tools/sap-pm-spare-parts-reorder-point-calculator
> Publisher: Netray (netray.co), AI and integration engineering for ERP and manufacturing systems.
> Section: Free Tools

## Short answer

Size reorder point, safety stock, economic order quantity and max stock for a maintenance spare, ready to enter in the SAP material master MRP view.

## Category

sap

## Erp

SAP PM

## Industry

Manufacturing

## Audience

- Maintenance planner
- MRO buyer
- SAP MM consultant

## Tool

**Kind:** calculator

**Currency:** $

**Inputs:**

#### Average demand per month

**Key:** demand_month

**Type:** number

**Default:** 6

**Min:** 0

**Step:** 0.5

**Unit:** units

#### Std deviation of monthly demand

**Key:** sigma_month

**Type:** number

**Default:** 3

**Min:** 0

**Step:** 0.5

**Unit:** units

#### Replenishment lead time

**Key:** lead_time

**Type:** slider

**Default:** 30

**Min:** 1

**Max:** 180

**Step:** 1

**Unit:** days

#### Target service level

**Key:** service

**Type:** select

**Default:** 0.95

**Options:**

##### 90%

**Value:** 0.9

##### 95%

**Value:** 0.95

##### 97.5%

**Value:** 0.975

##### 99%

**Value:** 0.99

#### Unit cost

**Key:** unit_cost

**Type:** number

**Default:** 185

**Min:** 0.01

**Step:** 5

**Unit:** per unit

#### Cost to place an order

**Key:** order_cost

**Type:** number

**Default:** 60

**Min:** 0

**Step:** 5

**Unit:** per order

#### Annual holding cost rate

**Key:** hold_rate

**Type:** number

**Default:** 22

**Min:** 1

**Max:** 60

**Step:** 1

**Unit:** %

**Outputs:**

#### Average daily demand

**Key:** demand_day

**Expr:** demand_month / 30

**Format:** decimal

#### Z score

**Key:** z

**Expr:** normsinv(service)

**Format:** decimal

#### Safety stock

**Key:** ss

**Expr:** ceil(z * (sigma_month / sqrt(30)) * sqrt(lead_time))

**Format:** integer

**Primary:** true

**Description:** Enter in the Safety stock field of the MRP 2 view.

#### Reorder point

**Key:** rop

**Expr:** ceil(demand_day * lead_time + ss)

**Format:** integer

**Primary:** true

**Description:** Enter in the Reorder point field for MRP types VB or VM.

#### Economic order quantity

**Key:** eoq

**Expr:** ceil(sqrt(2 * demand_month * 12 * order_cost / (unit_cost * hold_rate / 100)))

**Format:** integer

#### Maximum stock level

**Key:** max_stock

**Expr:** rop + eoq

**Format:** integer

**Description:** Use as the target ceiling when replenishing by a fixed lot.

#### Safety stock value

**Key:** ss_value

**Expr:** ss * unit_cost

**Format:** currency

**Chart:**

#### Safety stock and reorder point vs lead time (days)

**Type:** line

**X:** lead_time

**From:** 5

**To:** 120

**Steps:** 24

**Series:**

- ss
- rop

**Disclaimer:** Assumes normally distributed demand and constant lead time. Critical insurance spares with very low usage need a risk-based decision instead.

## Content

**Intro:** Maintenance spares behave differently from production components: demand is lumpy, lead times are long and a stockout stops a line. This calculator gives a defensible reorder point, safety stock and order quantity for the parts that actually move.

**Sections:**

#### How to use it

**Body:** Take twelve months of goods issues from reservations against maintenance orders for the material, and compute the monthly average and standard deviation. Enter the vendor lead time including receiving, a service level and the cost figures. Copy the safety stock and reorder point into the material master MRP view for the plant, and set an MRP type such as VB for manual reorder point planning.

**Bullets:**

- Use consumption statistics, not purchase history, for demand.
- Strip out one-off shutdown consumption before taking the mean.
- Use the lead time that includes inspection and put-away.

#### The formulas

**Body:** Safety stock equals the Z score for the service level times daily demand deviation times the square root of lead time. Reorder point equals daily demand times lead time plus safety stock. Economic order quantity equals the square root of two times annual demand times order cost divided by unit cost times holding rate. Maximum stock is reorder point plus order quantity, a common ceiling for fixed-lot replenishment.

#### Where this does and does not apply

**Body:** This method suits fast and medium moving consumables such as bearings, filters, belts and seals. It is a poor fit for insurance spares like a motor or gearbox, where you stock on criticality and lead time rather than average demand. For those, use a risk review and a one-line min-max of one. Check also whether your vendor offers consignment or a vendor-managed stock.

**Bullets:**

- Revisit parameters after every large change in demand or lead time.
- Use rounded vendor pack sizes when setting the lot size.
- Flag parts with no movement in 24 months for review.

**Cta:** If you want safety stock and reorder points recalculated from live consumption and written back for approval, Netray can build that with a human approval step.

**Faq:**

#### Which SAP MRP types use a reorder point?

**Answer:** Manual reorder point planning uses MRP type VB, and automatic reorder point planning uses VM, where the system calculates the reorder point from consumption and forecast. Both read the safety stock and reorder point on the MRP view.

#### How do I get demand standard deviation?

**Answer:** Export monthly goods issues for the material over at least 12 months and use the sample standard deviation in Excel. Remove outliers such as one-off projects before calculating.

#### Does safety stock cover lead time variability?

**Answer:** This tool covers demand variability only. If vendor lead times vary a lot, increase the lead time input toward the realistic late case, or use a combined variance formula.

#### Should every spare use this calculator?

**Answer:** No. Critical, low usage insurance spares are best chosen by consequence of failure and replacement lead time, not average demand. Use criticality ranking first, then calculate only for consumables.

## Search terms

spare parts reorder point calculator, mro safety stock calculator, sap reorder point vb vm, maintenance spares min max, eoq calculator spare parts, sap pm spare parts stocking, safety stock formula lead time variability, mro inventory optimisation

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