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FREE INVENTORY ANALYSIS TOOL

Inventory Aging Calculator

Analyze inventory by age, measure how much value is tied up in older stock, and identify aging SKUs that may need closer review.

  • Free to use
  • No sign-up required
  • Built for real inventory decisions

Calculator

Aging Threshold Settings

Inventory Age uses a consistent measure such as days since receipt, batch age, or another internal standard. It is not Days Since Last Sale.

Paste Spreadsheet Data Paste tab-separated or comma-separated rows

SKU [tab] Product Name [tab] Current Stock [tab] Unit Cost [tab] Inventory Age

Multi-SKU Workspace

Enter up to 20 SKUs. No-on-hand-stock rows stay visible but do not affect age exposure.

8 / 20 rows
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Results

Calculated
Aged Inventory Value$14,000

70% of the analyzed inventory value is older than the current 90-day aging threshold.

Total SKUs8Valid SKU rows analyzed
Total Inventory Value$20,000Current stock × unit cost
Value-Weighted Average Age153 daysWeighted by inventory value
Aged Inventory Share70%Older than 90 days

Decision metrics

Aged Inventory Value$14,000Older than 90 days
Old Inventory Value$6,000Older than 180 days
Old Inventory Share30%Of total analyzed inventory value
Aging + Old SKUs5Older than the aging threshold
Oldest SKUSKU-H400 days
Highest-Value Aging SKUSKU-D$4,500
Decision Insight

$14,000 of inventory value is older than 90 days, representing 70% of the analyzed inventory value. $6,000 is older than 180 days. SKU-D is the highest-value aging item at $4,500. Older inventory should be reviewed alongside sales velocity, seasonality, demand forecasts, and strategic importance before action is taken.

Inventory Aging Summary

Inventory value and share by age bucket.

Fresh0–30 days1 SKU$1,0005%
Recent31–60 days1 SKU$3,00015%
Watch61–90 days1 SKU$2,00010%
Aging91–180 days2 SKUs$8,00040%
Old181+ days3 SKUs$6,00030%

Aging Distribution

Inventory value by age bucket.

Inventory Aging Analysis

Old, Aging, and Watch items receive priority in that order, then by inventory value.

1Priority 1SKU-FProduct F100 units$30$3,000220 daysOld15%
2Priority 2SKU-GProduct G100 units$20$2,000300 daysOld10%
3Priority 3SKU-HProduct H50 units$20$1,000400 daysOld5%
4Priority 4SKU-DProduct D150 units$30$4,500120 daysAging22.5%
5Priority 5SKU-EProduct E175 units$20$3,500160 daysAging17.5%
6Priority 6SKU-CProduct C100 units$20$2,00075 daysWatch10%
7—SKU-BProduct B100 units$30$3,00045 daysRecent15%
8—SKU-AProduct A50 units$20$1,00015 daysFresh5%

Key Takeaways

  • Inventory aging measures how long inventory has remained in stock under the age definition you use.
  • Value-weighted aging helps highlight older inventory with greater financial exposure.
  • Older inventory deserves review, but age alone does not prove an item is obsolete or dead stock.
  • Combine aging with sales velocity, seasonality, demand forecasts, and strategic importance before taking action.

How It Works

Calculate inventory value for each SKU.

Assign each SKU to an aging bucket based on its inventory age.

Measure the value and share of every age bucket, then calculate value-weighted average inventory age.

Prioritize older inventory by age bucket and inventory value. Inventory Age should use one consistent definition across your data.

Formula

Formula 1

Inventory ValueCurrent Stock × Unit Cost

Formula 2

Value-Weighted Average AgeΣ(Inventory Value × Inventory Age) ÷ Total Inventory Value

Formula 3

Bucket ValueΣ Inventory Value for SKUs in the selected age bucket

Formula 4

Bucket Value ShareBucket Value ÷ Total Inventory Value × 100

Formula 5

Aged Inventory ValueΣ Inventory Value where Inventory Age > Aging Threshold

Formula 6

Old Inventory ValueΣ Inventory Value where Inventory Age > Old Inventory Threshold

Where:

  • Inventory Age: a consistent age measure such as days since receipt, batch age, or another internal standard.
  • Age Buckets: the ranges created by your four configurable threshold settings.
  • Aged Inventory: inventory older than Threshold 3.
  • Old Inventory: inventory older than Threshold 4.

Example Calculation

Let’s say:

  • SKU-D: 150 units × $30 = $4,500; age 120 days
  • SKU-F: 100 units × $30 = $3,000; age 220 days
With thresholds of 30 / 60 / 90 / 180 days, SKU-D is Aging and SKU-F is Old. The default data produces $14,000 aged inventory, $6,000 old inventory, and a value-weighted average age of 153 days.

Inventory Age is different from Days Since Last Sale: aging measures how long stock has remained under your selected age definition, while Dead Stock screens inactivity.

How to Use the Result

  • Review Old and Aging inventory before placing additional replenishment orders.
  • Prioritize older items with higher inventory value for closer analysis.
  • Compare aging results with sales velocity and Dead Stock results before deciding on markdowns, transfers, returns, or liquidation.
  • Check whether old inventory is seasonal, strategic, required as spare stock, or subject to long replenishment cycles.
  • Re-run aging analysis regularly as stock is sold, replenished, or revalued.

Limitations

  • Inventory age depends on the aging definition and source data used by the business.
  • A single SKU can contain units from multiple receipt dates, so one SKU-level age may simplify lot-level reality.
  • Older inventory is not automatically obsolete, excess, or dead stock.
  • Seasonal, spare-part, strategic, or slow-cycle inventory may legitimately remain in stock for long periods.
  • Unit cost determines financial exposure and should use a consistent valuation basis.
  • Thresholds are configurable guidelines, not universal standards.
  • The tool does not automatically include sales velocity, forecasts, supplier lead times, future promotions, or strategic importance.
  • No-On-Hand-Stock rows are excluded from aging exposure calculations.

Frequently Asked Questions

What is inventory aging?

Inventory aging describes how long inventory has remained in stock using a consistent age definition chosen by the business.

How do you calculate inventory age?

Use one consistent measure such as days since receipt, batch age, or another internal inventory-age standard.

What are common inventory aging buckets?

30, 60, 90, and 180 days are common starting points, but the right buckets depend on the business and product cycle.

What does inventory over 90 days mean?

It means the item exceeds the current 90-day threshold. It is a signal for review, not an automatic disposal decision.

What is the difference between inventory aging and dead stock?

Aging measures stock age. Dead stock evaluates inactivity such as days since last sale and recent sales velocity.

Is old inventory always bad?

No. Seasonal, spare, strategic, and slow-cycle items can be legitimately old.

How often should inventory aging be reviewed?

Review it regularly and after material changes to stock, demand, valuation, or product mix.

How does inventory aging affect working capital?

Older stock can tie up capital for longer, especially when it carries a high inventory value.

What should I do with aging inventory?

Review the cause, seasonality, demand outlook, and strategic importance before deciding on any action.

Can seasonal inventory appear old?

Yes. Seasonal inventory can remain in stock for long periods and still be appropriate.

Should inventory aging be based on receipt date or last sale date?

Use receipt or batch age for aging. Last-sale timing belongs in an inactivity or dead-stock analysis.

What is value-weighted inventory age?

It weights every SKU age by inventory value so older, higher-value stock contributes more to the overall exposure measure.