ABC Analysis Calculator
Classify inventory into A, B, and C categories based on annual value using Pareto analysis to prioritize stock management efforts.
Weeks of Supply Calculator
Calculate how many weeks your current inventory will cover based on average weekly usage. Ideal for medium-term supply planning.
units
units/wk
$
weeks
weeks
Weeks of Supply⧉
5.0
Inventory ÷ Weekly usage = 5,000.00 ÷ 1,000.00 = 5.0 wks
Days of Supply⧉
35.0
5.0 weeks × 7 = 35.0 days
Months of Supply⧉
1.15
5.0 weeks ÷ 4.33 weeks/month
Inventory Value⧉
$75,000.00
5,000.00 units × $15.00 per unit
Inventory Turns / Year⧉
10.4
52 × weekly usage ÷ inventory. Higher = more capital-efficient
Annual Carrying Cost⧉
$18,750.00
25% of inventory value — includes storage, insurance, obsolescence
Pipeline Stock⧉
2,000 units
Lead time (2.00 wks) × weekly usage — in-transit inventory
Vs. Target Gap⧉
-1,000 units
$15,000.00 below target — replenish soon
Weeks of Supply vs. Target
5.0 weeksTarget: 6 weeks
Forward Coverage Analysis
| Horizon | Units Needed | Covered? | Surplus / Shortfall |
|---|---|---|---|
| 2 weeks | 2,000.00 | ✓ Yes | +3,000.00 |
| 4 weeks | 4,000.00 | ✓ Yes | +1,000.00 |
| 6 weeks | 6,000.00 | ✗ No | −1,000.00 |
| 8 weeks | 8,000.00 | ✗ No | −3,000.00 |
| 12 weeks | 12,000.00 | ✗ No | −7,000.00 |
| 16 weeks | 16,000.00 | ✗ No | −11,000.00 |
| 20 weeks | 20,000.00 | ✗ No | −15,000.00 |
| 26 weeks | 26,000.00 | ✗ No | −21,000.00 |
Carrying Cost: Current vs. Target
| Metric | Current | At Target (6 wks) | Difference |
|---|---|---|---|
| Inventory (units) | 5,000.00 | 6,000.00 | -1,000.00 |
| Inventory Value | $75,000.00 | $90,000.00 | -$15,000.00 |
| Annual Carrying Cost | $18,750.00 | $22,500.00 | -$3,750.00 |
Planning notes, formulas, and examples
About the Weeks of Supply Calculator
Weeks of supply (WOS) measures how many weeks your current inventory will last at the present rate of weekly consumption. While days of supply is preferred for fast-moving items, many supply chain planners find weeks of supply more practical for medium- and long-lead-time products, seasonal planning, and executive-level inventory reporting.
The formula is simply average inventory divided by average weekly usage. A WOS of 4 means you have roughly one month of stock coverage. Most businesses target WOS between 2 and 8 weeks, depending on lead times, demand variability, and service level requirements.
Enter your average inventory and average weekly usage to compute your weeks of supply, along with the equivalent days of supply for detailed planning.
Use the result to compare operating scenarios, pressure-test assumptions, and rerun the model when volumes, rates, or service targets change.
When This Page Helps
Weeks of supply puts inventory levels into a human-friendly time frame that aligns with weekly planning cycles, S&OP meetings, and supplier order schedules. It is the preferred coverage metric in industries with weekly or bi-weekly replenishment cadences, such as retail, CPG, and wholesale distribution.
How to Use the Inputs
- Enter the average inventory on hand (in units or dollars).
- Enter the average weekly usage or demand.
- Review the calculated weeks of supply.
- Compare WOS against your lead time in weeks to check coverage adequacy.
- Identify SKUs with WOS significantly above target for potential reduction.
- Track WOS trends weekly in your S&OP dashboard.
Formula used
Weeks of Supply = Average Inventory / Average Weekly Usage
Days of Supply = WOS × 7
Where:
Average Inventory = on-hand stock (units or $)
Average Weekly Usage = units sold or consumed per weekExample Calculation
Result: WOS = 5.0 weeks
Weeks of Supply = 5,000 units / 1,000 units per week = 5.0 weeks. At the current consumption rate, you have five full weeks of inventory coverage before stock runs out.
Tips & Best Practices
- For seasonal products, use the upcoming season's weekly forecast, not historical averages.
- Target WOS should cover lead time in weeks plus a safety buffer.
- Compare WOS across product categories to identify where capital is over-allocated.
- Use WOS as a common language between operations, finance, and merchandising.
- Alert on WOS falling below 2 weeks for fast-moving essential items.
- For S&OP reporting, present WOS at the category or brand level for clarity.
WOS in Executive Reporting
Weeks of supply is a staple of executive dashboards because it conveys inventory health in an immediately understandable time unit. CFOs look at WOS to assess working capital efficiency. VPs of Supply Chain use it to identify categories needing attention.
Forward-Looking WOS
Instead of dividing by historical weekly usage, advanced planners divide by forecasted weekly demand. This gives a forward-looking WOS that accounts for anticipated promotions, seasonal shifts, or demand trends, providing a more accurate picture of future coverage.
WOS Targets by Category
Set differentiated WOS targets by ABC class or product lifecycle stage. A-items may target 2-3 weeks, B-items 4-5 weeks, and C-items 6-8 weeks. New product launches may start with higher WOS until demand stabilizes.
Reducing WOS Without Stockouts
The key is to reduce the numerator (average inventory) without proportionally affecting service. Tactics include smaller, more frequent orders, better forecasting to reduce safety stock, vendor-managed inventory, and cross-docking programs that move goods through the DC faster.
Sources & Methodology
Last updated:
Frequently Asked Questions
Weeks of supply is the number of weeks your current inventory will last at the current weekly consumption rate. It is the weekly counterpart of days of supply and a standard metric in S&OP processes.
It varies by industry and item. Fast-moving consumer goods aim for 2-4 weeks, while specialty items with long lead times may target 6-10 weeks. Set targets relative to lead time and demand variability.
WOS = DOS / 7. If you have 35 days of supply, that is 5 weeks. Choose whichever metric suits your planning cadence and audience.
Yes, include total on-hand inventory. Safety stock is part of your physical stock and contributes to coverage. Some planners also compute WOS excluding safety stock to see available coverage beyond the buffer.
Sum units sold or consumed over a representative period (typically 4-12 weeks) and divide by the number of weeks. Filter out anomalies like promotion spikes for a more stable average.
Yes, if demand is highly seasonal. In the off-season, WOS appears high because weekly usage is low, even though you may be building stock for a peak season. Always interpret WOS in the demand context.
Improve demand forecasting, reduce supplier lead times, order more frequently in smaller quantities, and tighten safety stock calculations. Each strategy reduces average inventory relative to consumption.
WOS is one of the most common metrics in Sales & Operations Planning. It provides a simple, actionable view of inventory health that bridges the gap between supply chain detail and executive-level strategy.
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