💰 Finance calculator

Average Inventory Calculator

Calculate average inventory from beginning and ending balances — then go further with inventory turnover ratio, days inventory outstanding (DIO), a benchmark zone indicator, and period-over-period trend bars. Optionally add a previous period to see whether inventory efficiency is improving or declining.

Enter inventory values

Use a preset or enter your own values. COGS is optional — add it to unlock turnover ratio and DIO. The prior-period inputs are also optional — add them for trend comparison.

🟢 Current period
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Opening stock value at start of period
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Closing stock value at end of period
⚪ Optional — turnover & DIO
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Same period as inventory — unlocks turnover & DIO
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365 = annual · 90 = quarterly · 30 = monthly
⚪ Optional — prior period comparison
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For period-over-period trend
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For period-over-period trend
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For prior period turnover comparison

Core formulas

Avg inventory = (Beginning + Ending) ÷ 2
Turnover = COGS ÷ Avg inventory
DIO = Period days ÷ Turnover
DIO alt = (Avg inv ÷ COGS) × Period days

Why average, not ending?

Using only ending inventory in turnover inflates the ratio if the period ends with unusually low stock. Average inventory smooths the balance, giving a fairer picture of how much inventory the business actually carried during the period — not just at one snapshot.

Tip: for seasonal businesses, a simple 2-point average (beginning + ending) may still misrepresent true average stock levels. If monthly data is available, use a 12-point monthly average for a more accurate picture — add all 12 month-end balances and divide by 12.
This calculator is for planning and educational purposes only. Actual inventory analysis may require monthly averages, weighted averages, seasonal adjustments, FIFO/LIFO/weighted average cost considerations, or more detailed stock movement data depending on the business and accounting policy.

Frequently asked questions

What is the average inventory formula?

Average inventory = (Beginning inventory + Ending inventory) ÷ 2. For multi-period data, average inventory = sum of all period-end balances ÷ number of periods. The 2-point formula is standard for quarterly and annual calculations.

What is days inventory outstanding (DIO)?

DIO measures how many days on average a business holds inventory before it is sold. DIO = Period days ÷ Inventory turnover, or equivalently (Average inventory ÷ COGS) × Period days. Lower DIO = faster-moving inventory. Higher DIO = slower turnover, which ties up more working capital.

What is a healthy inventory turnover ratio?

It varies significantly by industry. Grocery and FMCG businesses typically see turnover of 12–30× per year. General retail averages 4–8×. Manufacturing typically runs 4–6×. Luxury goods may be 1–3×. The most meaningful benchmark is your own trend over time and comparison with direct competitors, not a generic number.

Can I use this calculator for a quarterly period?

Yes. Select "Quarterly (90 days)" from the period length dropdown. DIO will then be calculated as (Average inventory ÷ COGS) × 90. Make sure the COGS figure you enter covers the same 90-day period as your inventory balances.

Related finance calculators

Weeks of Supply Calculator Calculate inventory coverage in weeks — complementary to DIO for supply chain planning. Cost Per Item Calculator Calculate unit cost — the per-unit figure that drives total inventory value on the balance sheet. Cost Savings Calculator Quantify the working capital freed up by reducing average inventory or improving turnover. Retained Earnings Calculator Connect inventory efficiency to profitability — better turnover feeds directly into earnings retention.

Disclaimer

This calculator is for educational and planning purposes only. It does not provide accounting, tax, audit, or financial advice. Actual inventory analysis may differ based on costing method (FIFO, LIFO, weighted average), accounting policy, seasonality, and how inventory is classified or measured in your financial statements.