01
Enter current stock and average daily sales
Units on hand today and average units sold per day over the past 30–90 days. These two numbers produce the core coverage figure.
Stock Coverage Calculator
See how many days your stock will last and whether a stockout is coming.
Updated Reviewed by Sajid Hussain· Editor
Try it with your numbers
Results update in real time as you type — no submit needed.
Your numbers
Results
⚡
Results appear as you type
No submit button needed
Why trust this calculator
Last updated
June 9, 2026
Coverage
9 markets · 8 currencies
Privacy
Calculated in-browser · no data stored
Pricing
Free forever · no sign-up
Know your coverage in seconds
Stock coverage calculator — how long will your stock last?
Stock coverage days (also called days of inventory on hand or DOH) measures how long your current inventory will last at the current average daily sales rate. It is the most immediate snapshot of inventory health — too few days and you risk stockout; too many and you have capital tied up in excess stock. This calculator shows your coverage in days and weeks, flags stockout risk and overstock, and quantifies the revenue or capital at stake.
Coverage days = current stock ÷ average daily sales. A store with 500 units selling 10 units per day has 50 days of coverage. If the supplier lead time is 30 days, that gives 20 days of margin before reorder becomes urgent — enough of a buffer unless demand spikes.
The two most important thresholds are your lead time (the minimum coverage needed to avoid a stockout) and your target coverage (the optimal level that balances capital efficiency with safety). Coverage below lead time is an emergency. Coverage above 1.5× target is a sign of overordering.
Revenue at risk quantifies the business impact of a stockout. If you run out of stock 10 days before your next shipment arrives and you sell 10 units per day at 30 each, you miss 3,000 in revenue. On Amazon this also triggers ranking penalties that persist after restocking.
Excess inventory value shows the cost of the capital tied up in overstock. If you hold 400 units more than your 60-day target and each unit cost 12, that is 4,800 of capital earning no return — and accumulating carrying cost every week.
Quick facts
- Coverage in days and weeks
- Current stock ÷ average daily sales
- Stockout risk flag
- When coverage < lead time
- Overstock flag
- When coverage > 1.5× target
- Revenue at risk
- Quantified for stockout scenarios
- Excess inventory value
- Capital cost of overstock position
- Ideal stock level
- Target coverage × daily sales rate
How it works
Six inputs, an instant inventory health check
Enter your stock, sales rate, and targets — your coverage and risk status are ready immediately.
02
Set your lead time
How many days from placing an order to receiving stock. This is the stockout risk threshold — if coverage falls below this, you need to order now.
03
Set your target coverage
The ideal days of stock you want to hold. Typically 30–90 days for ecommerce depending on lead time variability and capital efficiency targets.
04
Add selling price and cost per unit (optional)
Used to quantify revenue at risk from a stockout and the cost of excess inventory. Leave at defaults if you only need the coverage day count.
05
Read your coverage and status
The calculator shows days and weeks of coverage, whether you face a stockout or overstock, the revenue at risk or excess inventory value, and your ideal stock level.
Steps to use the Stock Coverage Calculator: Enter current stock and average daily sales, Set your lead time, Set your target coverage, Add selling price and cost per unit (optional), Read your coverage and status.
Formula
The stock coverage formula, step by step
Simple division plus two threshold checks — transparent math you can verify by hand.
01
Days of stock coverage
Days of Coverage = Current Stock ÷ Average Daily Sales
How many days your current inventory will last at the current average sell rate. The core metric.
Example: 500 units ÷ 10 units/day = 50 days of coverage
02
Stockout risk check
Stockout Risk = Days of Coverage < Lead Time Days
If you will run out of stock before the next order arrives, you face a stockout. The lead time is the critical minimum coverage threshold.
Example: 50 days coverage vs 60-day lead time → stockout risk (50 < 60)
03
Overstock check
Overstocked = Days of Coverage > Target Coverage Days × 1.5
If you have significantly more stock than your target, capital is being wasted on excess inventory. The 1.5× multiplier allows a reasonable buffer above target before flagging.
Example: 200 days coverage vs 60-day target × 1.5 = 90-day threshold → overstocked (200 > 90)
04
Revenue at risk
Revenue at Risk = max(0, Lead Time Days − Days of Coverage) × Avg Daily Sales × Selling Price
The revenue missed during the stockout window — the days you run dry before the next shipment arrives. Only applies when coverage < lead time.
Example: (60 − 50) days × 10 units/day × 30 = 3,000 revenue at risk
05
Ideal stock and excess inventory
Ideal Stock = Target Coverage Days × Avg Daily Sales | Excess = max(0, Current Stock − Ideal Stock)
The ideal stock level matches your target coverage exactly. Excess is everything above it — valued at cost to show the capital tied up.
Worked example
500 units, 10/day, 30-day lead, 60-day target
See how coverage, shortfall, and risk are calculated from a typical ecommerce inventory position.
Scenario
A seller has $500.00 units in stock, sells $10.00 units per day on average, with a $30.00-day lead time and a $60.00-day target coverage. Is their stock position healthy?
1
Step 1 · Days of coverage
$500.00 units ÷ $10.00 units/day = 50.0 days of stock.
50.0 days of coverage (7.1 weeks)
2
Step 2 · Stockout risk check
50.0 days coverage vs $30.00-day lead time → 50.0 > $30.00 → no stockout risk.
No stockout risk
3
Step 3 · Overstock check
50.0 days vs $60.00-day target × 1.5 = 90-day threshold → 50.0 < 90 → not overstocked.
Not overstocked
4
Step 4 · Shortfall vs target
Ideal stock: $60.00 days × $10.00/day = 600 units. Shortfall: 600 − $500.00 = 100 units below target.
100 units below the 60-day target
The takeaway
With 50 days of coverage, the position is healthy but 100 units below the 60-day target. No stockout risk (30-day lead time is well covered) and not overstocked. The seller should plan their next order to top up to the 600-unit target within the next 20 days (before they hit the reorder point).
Industry benchmarks
Target coverage days by business model and category
Optimal stock coverage varies by sourcing strategy, product category, and lead time. Use these benchmarks to calibrate your target coverage days input.
| Metric | Poor | Average | Good | Excellent |
|---|---|---|---|---|
Overseas-sourced (China, India) — FBA Jungle Scout Amazon Seller Report 2025 | < 45 days | 45–60 days | 60–90 days | 90+ days pre-peak |
Domestic / 3PL-fulfilled ShipBob Ecommerce Fulfillment Report 2024 | < 14 days | 14–30 days | 30–60 days | 60+ days for stable SKUs |
Grocery / perishables Food Marketing Institute Supermarket Facts 2024 | > 14 days | 7–14 days | 3–7 days | < 3 days (fresh) |
Fashion / seasonal apparel NRF Retail Benchmarks 2025 | < 30 days or > 120 days | 30–60 days | 60–90 days in season | Near-zero at end of season |
Electronics / tech accessories Gartner Supply Chain Top 25 2024 | > 90 days (obsolescence risk) | 45–90 days | 30–45 days | < 30 days (fast-turn model) |
Why this calculator
Calcrux vs spreadsheets vs RestockPro
Most sellers track days of stock in a basic spreadsheet with no risk thresholds, revenue-at-risk calculation, or overstock flag. Paid tools like RestockPro charge 49–199/month for similar features. This calculator delivers the same analysis free.
| Feature | Calcrux | Spreadsheet | RestockPro (paid) |
|---|---|---|---|
| Days of stock coverage | Manual | ||
| Weeks of coverage | |||
| Stockout risk flag vs lead time | |||
| Overstock flag vs target coverage | Partial | ||
| Revenue at risk calculation | Partial | ||
| Excess inventory value | Partial | ||
| Ideal stock level | Manual | ||
| Works without connected data | |||
| Free to use, no subscription | |||
| Works for any channel | Amazon focused |
Common mistakes
Where stock coverage calculations go wrong
Using total stock instead of sellable stock
Why it matters
Total stock may include reserved, damaged, or in-transit units that cannot actually be sold. Including non-sellable stock in the calculation overstates true coverage.
Fix
Use only units that are available to sell — on-hand, sellable inventory at your warehouse or FBA, excluding reserved, damaged, and in-transit stock.
Using total sales instead of average daily units
Why it matters
Monthly sales figures can hide huge day-to-day variability. A product that sold 500 units in 30 days but 400 of them in the last week is not a 16.7/day average — it is a fast-accelerating product that your coverage calculation underestimates.
Fix
Use a 30–90-day average to smooth variability. For fast-growing products, weight recent weeks more heavily or use the inventory forecast calculator's growth-adjusted rate.
Setting the same target coverage for every SKU
Why it matters
A high-velocity best-seller and a slow-moving long-tail SKU have very different optimal coverage targets. One size does not fit all — managing them the same leads to overstock on one and stockout on the other.
Fix
Segment SKUs by velocity and lead time. Fast movers with long lead times need higher target coverage. Slow movers can be managed with less cover and more frequent small orders.
Ignoring in-transit stock in the coverage calculation
Why it matters
If you have a purchase order already in transit, your effective coverage is current stock + in-transit stock ÷ daily rate. Omitting it makes coverage look lower than it really is and can trigger premature orders.
Fix
Add confirmed in-transit stock to current stock when calculating coverage. Treat it as arriving on the expected date minus a few days of buffer for delays.
Not checking coverage after a demand spike
Why it matters
If sales suddenly double for a week (a viral moment, flash sale, or influencer mention), coverage can drop from 50 days to 25 days overnight. A weekly coverage check misses this until it is too late.
Fix
Set up a daily or twice-weekly coverage review for your top revenue SKUs. Any time coverage drops more than 10 days in a week, investigate immediately.
Confusing coverage days with days until reorder
Why it matters
Coverage days tells you how long stock will last at current rate. Days until reorder tells you when to place the next order (when stock hits the reorder point = lead time demand + safety stock). They are related but different.
Fix
Use coverage days for the snapshot health check. Use the reorder point calculator for the precise trigger at which to place your next purchase order.
Tips
Getting more from your stock coverage analysis
Monitor top SKUs weekly
The 20% of SKUs that generate 80% of revenue deserve weekly coverage monitoring. A daily check during peak season or after a major promotion is not overkill for your best performers.
Alert at 1.5× lead time
When coverage drops to 1.5× your lead time, treat it as the trigger to initiate an order — not the ROP itself. This gives you a safety margin before you hit the true reorder point.
Prioritize by revenue at risk
When you have multiple SKUs with stockout risk and limited cash or shipping slots, prioritize by revenue at risk. The product with the largest expected lost revenue gets the first purchase order.
Compare excess to carrying cost
If you are overstocked, check how much the excess is costing you per month using the carrying cost calculator. That monthly number is the case for a promotion or markdown to clear excess stock.
Check before every buying cycle
Make stock coverage the first report you check before any purchase order. Coverage days tells you who needs restocking urgently and who has enough headroom to wait for the next order.
Adjust target coverage seasonally
Set a higher target coverage before your peak season (to pre-position stock) and a lower target in the off-season (to avoid overstock). The same 60-day target in January and September will cause different problems.
Use cases
When sellers use the stock coverage calculator
The Stock Coverage Calculator works across every stage of the workflow.
Inventory Manager / Operations Lead
An ops manager checks coverage for all active SKUs every Monday morning. Any SKU below 1.5× lead time gets flagged for immediate purchase order review.
Ecommerce Business Owner
A seller with 10,000 of available buying budget uses revenue at risk to rank all at-risk SKUs and allocates spending to the highest-risk products first.
Seasonal Brand / Category Manager
At the end of Q3, a seasonal decor brand calculates coverage for all SKUs against expected Q4 demand. Anything with over 6 months of coverage gets flagged for clearance before the new season.
Amazon FBA Seller
An Amazon FBA seller uses coverage days to decide which products to include in the next inbound shipment, prioritizing SKUs with less than 45 days of coverage.
Product Launch Manager
For a recently launched SKU, a seller checks coverage daily for the first 30 days to catch any unexpected demand acceleration before stock runs out.
Head of Merchandising / Buying
A seller finds a SKU with 180 days of coverage — 3× the 60-day target. Excess inventory value shows 4,800 of capital tied up. They run a 30% promotion to clear excess and free the capital for faster-turning products.
Glossary
Stock coverage terms explained
Every important term you'll encounter in this calculator and the broader topic.
- Days of stock coverage (DOH)
- How many days your current inventory will last at the current average daily sales rate. The core inventory health metric: current stock ÷ average daily sales.
- Days on hand (DOH)
- Another name for days of stock coverage — how many days of inventory you have on hand at the current sell rate.
- Target coverage days
- The desired days of stock you want to hold on hand — your optimal inventory level. Should be at least 1.5–2× your lead time for safety.
- Lead time
- Total days from placing a purchase order to receiving sellable stock. The minimum coverage days you must maintain to avoid a stockout.
- Stockout risk
- When coverage days are less than lead time days — you will run out of stock before the next order arrives. On Amazon, stockouts suppress ranking for days after restocking.
- Overstocked
- When coverage days significantly exceed the target — capital is tied up in excess inventory that is accruing carrying cost. Typically flagged when coverage > 1.5× target.
- Revenue at risk
- The sales revenue expected to be lost during a stockout window — (lead time days − coverage days) × daily sales × selling price.
- Ideal stock level
- The unit quantity that exactly matches your target coverage days: target coverage × average daily sales. The balanced position between stockout and overstock.
- Excess inventory value
- The cost value of units held above the ideal stock level — the capital tied up in overstock that could be deployed elsewhere.
Help & answers
Frequently asked questions
Everything you need to know about how the Stock Coverage Calculator works.
01What is stock coverage and how do you calculate it?
Stock coverage (days of inventory on hand) measures how long your current stock will last at the current average daily sales rate. The formula is: Days of Coverage = Current Stock ÷ Average Daily Sales. For example, 500 units at 10 units per day = 50 days of coverage.
02What is a good number of days of stock coverage?
Good coverage = at least 1.5× your supplier lead time, minimum. For overseas-sourced products (30–45-day lead time), 60–90 days is typical. For domestic-sourced products, 30–60 days. The hard rule: coverage must always exceed your lead time or you face a stockout.
03When is stockout risk flagged by this calculator?
Stockout risk is flagged when your days of coverage are less than your lead time. This means you will run out of stock before the next order arrives. The calculator also quantifies the revenue at risk — the sales you will miss during the stockout window.
04What is revenue at risk in a stockout?
Revenue at risk = (Lead Time Days − Days of Coverage) × Average Daily Sales × Selling Price. It estimates the sales revenue missed during the stockout gap — the days between running out of stock and receiving the next order. On Amazon, ranking penalties add further hidden revenue loss.
05When is inventory considered overstocked?
This calculator flags overstock when coverage days exceed your target coverage days × 1.5. For a 60-day target, that threshold is 90 days. Overstock ties up capital in inventory earning no return and accruing carrying costs.
06What is excess inventory value?
Excess inventory value is the cost of units held above your ideal stock level: (Current Stock − Ideal Stock) × Cost Per Unit. It shows the capital deployed in overstock that could be freed by clearing slow-moving inventory or pausing orders.
07What is the ideal stock level?
Ideal stock level = Target Coverage Days × Average Daily Sales. It is the exact unit count that gives you your target number of days of coverage at the current sell rate — the balanced position between stockout and overstock.
08How often should I check my stock coverage?
For your top 20% of SKUs (by revenue), check weekly — or daily during peak season or after promotions. For mid-tier and slow movers, monthly is usually sufficient. Set an alert when any SKU drops below 1.5× your lead time in coverage days.
09Does the stock coverage calculator work for Amazon FBA?
Yes. Enter your FBA-available units as current stock and use your total lead time (supplier + transit + FBA receiving) as the lead time input. The calculator shows whether your FBA position needs replenishment before the next inbound window.
10What is the difference between days of coverage and reorder point?
Days of coverage tells you how long stock will last at the current rate — a snapshot metric. The reorder point tells you the specific unit count at which to place a new order. They are related: when coverage days drop below lead time, you are at or below the reorder point. Use the reorder point calculator for the precise ordering trigger.
11Can this calculator handle in-transit stock?
You can manually add in-transit stock to your current stock figure to get a more accurate coverage calculation. For example, if you have 500 units on hand and 200 units in transit arriving in 10 days, you might enter 700 as your current stock to reflect the full position.
12How do I use the stock coverage calculator for seasonal products?
Adjust your target coverage days before each season. Before peak season, set a higher target (90+ days) to pre-position enough stock. After peak season, lower the target to avoid carrying excess stock into the slow period. Also update your average daily sales to reflect the relevant season's sell rate, not the full-year average.
Keep exploring
Related tools
Reorder Point Calculator
Calculate the exact inventory level to trigger your next order — no stockouts.
Open tool
Inventory Forecast Calculator
Project demand for 30–90 days with growth trend and seasonal adjustment.
Open tool
Dead Stock Calculator
Quantify dead stock costs and decide: liquidate, discount, or hold.
Open tool
Amazon FBA Restock Calculator
Reorder point, days to reorder, and order quantity — no spreadsheets needed.
Open tool
Category
Ecommerce Seller Operations
Subcategory
inventory operations
Availability
Global · 9 markets
Price
Free forever
Topics
stock coverage calculatordays of stock coverageinventory coverage calculatorhow long will stock lastdays on hand inventorystock days calculatorinventory coverage ratioecommerce stock coveragedoh calculator inventorycoverage days stockinventory run ratestock coverage days formula
Explore 500+ more tools
Calculators, simulators, and decision tools for every stage of business operations.