Days of Inventory on Hand:
Formula & What’s a Good Number
Days of inventory on hand (DOH) tells you how long your current stock would last at today’s sales rate. The formula, sensible benchmarks, and the two directions the number can go wrong.
By Replenagise · Updated 11 July 2026 · 4 min read
The DOH formula
Days of Inventory on Hand = (Average Inventory Value ÷ Cost of Goods Sold) × 365
Or, per SKU in units: current stock ÷ average daily unit sales. Hold £50,000 of stock (at cost) against £300,000 annual COGS and DOH = (50,000 ÷ 300,000) × 365 ≈ 61 days — two months of cover. It is the inverse of inventory turnover (DOH = 365 ÷ turnover), which is why the two metrics always tell the same story from opposite ends.
Reading the number
What “good” looks like
Most ecommerce businesses land between 30 and 90 days. Fast-moving, easily-resupplied lines can run 20–40; long-lead-time imports justify 60–120. The benchmark that matters is your supplier lead time plus a demand-spike buffer — not someone else’s average.
Too high: cash asleep on shelves
DOH creeping up while sales hold steady means over-buying or dying lines. 150 days of cover is five months of cash you cannot spend, storage you are paying for, and markdown risk compounding quietly.
Too low: living on the edge
DOH below your supplier lead time is a stockout with a date on it — if replenishment takes 45 days and you hold 20 days of stock, arithmetic does the rest. Chronic low DOH on best sellers is lost revenue dressed up as efficiency.
Watch it per SKU, not just in total
A healthy 60-day blended average can hide 300-day dead stock and 10-day best sellers cancelling each other out. The distribution is the diagnosis; the average is just the headline.
From metric to action
DOH is a thermometer, not a treatment. The action layer is per-SKU: lines with high DOH need clearing or smaller reorders; lines with DOH inside lead time need a PO today. That per-SKU days-of-stock view — recalculated live and tied to reorder triggers — is exactly what Replenagise’s dashboard shows for every product, synced from Shopify and Linnworks.
Pair DOH with its sibling, the inventory turnover ratio, for the annual view of the same health check — and let the reorder engine keep both numbers where you want them.
Cluster mates: the inventory turnover ratio is the same health check annualised, sell-through rate judges each buy, and inventory forecasting software keeps all three where you want them.
Days of Inventory — FAQs
How do you calculate days of inventory on hand?
Divide average inventory value (at cost) by annual COGS and multiply by 365. Per SKU, the quick version is current units in stock ÷ average daily unit sales. Both answer: at the current sales rate, how many days until the shelf is empty?
What is a good days of inventory on hand?
For most ecommerce sellers, 30–90 days. Calibrate to your supply chain: comfortably above your supplier lead time (so you can replenish before running out), but not so far above it that cash sits idle — every extra 30 days of cover is a month of stock value tied up.
Is DOH the same as days sales of inventory (DSI)?
Yes — days of inventory on hand, days inventory outstanding (DIO), and days sales of inventory (DSI) are the same metric under different names: how many days of sales your current inventory represents at cost.
How do I reduce days of inventory on hand?
Reorder smaller and more often (see EOQ trade-offs), clear dead and slow stock, and size purchases from demand forecasts instead of supplier minimums where possible. Replenagise automates the buying side — order quantities track forecast demand, so cover stops drifting upward.
Days of Stock, Live, on Every SKU
Per-SKU days-of-stock with reorder triggers built in — synced live from Shopify and Linnworks.