# Shelf-Life Material Expiry Write-Off Calculator (Sealants, Adhesives, Prepreg)

> Source: https://netray.co/tools/aerospace-shelf-life-material-expiry-write-off-calculator
> Publisher: Netray (netray.co), AI and integration engineering for ERP and manufacturing systems.
> Section: Free Tools

## Short answer

Shows how much shelf-life controlled material expires before use for a given order size, and the yearly write-off that follows.

## Category

supply-chain

## Industry

Aerospace

## Audience

- Materials manager
- Buyer
- Planner

## Tool

**Kind:** calculator

**Inputs:**

#### Annual usage

**Key:** annual_usage

**Type:** number

**Default:** 2400

**Min:** 1

**Step:** 50

**Unit:** units

#### Unit cost

**Key:** unit_cost

**Type:** number

**Default:** 85

**Min:** 0

**Step:** 1

#### Total shelf life from manufacture

**Key:** shelf_life

**Type:** number

**Default:** 12

**Min:** 1

**Step:** 1

**Unit:** months

#### Life remaining when received

**Key:** remaining_pct

**Type:** number

**Default:** 75

**Min:** 1

**Max:** 100

**Step:** 5

**Unit:** %

**Help:** Supplier delivers with this share of the shelf life left.

#### Minimum life required at point of use

**Key:** min_life

**Type:** number

**Default:** 1

**Min:** 0

**Step:** 0.5

**Unit:** months

**Help:** Material below this is not allowed on the part.

#### Order quantity

**Key:** order_qty

**Type:** number

**Default:** 600

**Min:** 1

**Step:** 50

**Unit:** units

**Outputs:**

#### Monthly usage

**Key:** monthly

**Expr:** annual_usage / 12

**Format:** decimal

#### Usable months after receipt

**Key:** usable_months

**Expr:** max(0, shelf_life * remaining_pct / 100 - min_life)

**Format:** decimal

#### Largest order that avoids expiry

**Key:** max_safe_qty

**Expr:** monthly * usable_months

**Format:** integer

**Primary:** true

**Description:** Assumes steady use with first-expired-first-out.

#### Expired units per order

**Key:** expired

**Expr:** max(0, order_qty - max_safe_qty)

**Format:** integer

#### Annual write-off

**Key:** annual_writeoff

**Expr:** annual_usage / order_qty * expired * unit_cost

**Format:** currency

**Primary:** true

**Chart:**

#### Annual write-off vs order quantity

**Type:** line

**X:** order_qty

**From:** 100

**To:** 2400

**Steps:** 40

**Series:**

- annual_writeoff

**Currency:** $

**Disclaimer:** Assumes constant consumption and FEFO issue. Real demand is lumpy, so treat results as a planning guide and confirm limits against the material specification and your shelf-life extension procedure.

## Content

**Intro:** Sealants, adhesives, prepreg, films and some paints carry a hard expiry. Buy too much and the surplus is scrapped; buy too little and the line stops. This calculator finds the largest order that will be used before expiry and prices what happens when you order more.

**Sections:**

#### How to use it

**Body:** Enter annual usage and unit cost, the full shelf life, the share of life left on delivery, and the minimum life the process allows at point of use. Then try different order quantities. The result is the safe quantity, the expired units per order, and the yearly write-off. The chart sweeps order size so you can see where waste starts.

**Bullets:**

- Use cold-storage out-time limits separately, they are not shelf life.
- Update the remaining-life percentage from real receipt data.
- Re-run for each material, they behave very differently.

#### The method

**Body:** Usable months equal total life times the share remaining on receipt, minus the minimum life at use. Safe quantity is monthly usage times usable months. Anything above it expires before it can be consumed, and annual write-off is the number of orders per year times the expired units times unit cost. The model is intentionally simple so it can be checked by hand.

#### ERP notes

**Body:** Most ERPs track lot expiry dates and can issue by earliest expiry, but few warn when a purchase order quantity exceeds what demand can consume. Check planning parameters such as lot size, minimum remaining shelf life on goods receipt and the expiry-date fields on lot records. Freezer-controlled materials also need a record of thaw time and out-time.

**Cta:** If you want expiry risk flagged at purchase order time from live demand in your ERP, we can scope that with you.

**Faq:**

#### Does this model uneven demand?

**Answer:** No. It assumes steady monthly use. For lumpy demand, run the tool with a conservative usage figure or use the forecast for the next shelf-life window instead of annual average usage.

#### What is minimum remaining shelf life?

**Answer:** It is the least life a lot may have left when issued or received. Many sites use it as an acceptance rule at goods receipt, which stops short-dated material entering stock.

#### Can expired material be extended?

**Answer:** Sometimes, under a documented shelf-life extension program with retest data and customer or material specification approval. Never extend without that authority; the calculator treats expiry as final.

#### Why does a bigger order cost more here?

**Answer:** Because once the order exceeds what you can use in the usable window, the excess expires. Bigger orders may still win on unit price, so compare the write-off with the discount you are offered.

## Search terms

shelf life expiry calculator, prepreg shelf life write off, sealant shelf life management, expired inventory cost calculator, shelf life controlled material, order quantity shelf life, aerospace material expiry, FEFO inventory calculator

---
Talk to an engineer: https://netray.co/contact?intent=erp_ai | Machine catalog: https://netray.co/agent/catalog.json