Safety Stock Calculator
Enter average and maximum daily demand, average and worst-case lead times, service level target, and carrying cost. See recommended buffer units, its dollar value, annual holding cost, and how many days of demand it covers at average and peak. Compare buffers at 90%, 95%, and 99% service levels.
Instant calculations · Editable fee assumptions · Export-ready results
Inputs
Values update results instantly. Adjust fee assumptions to match your seller dashboard.
Demand
Average units sold per day
Peak daily demand observed
Supply
Average supplier lead time
Worst-case lead time observed
Target
Service level % — 95% means 5% chance of stockout
Reference
Purchase or manufacturing cost
Annual inventory carrying cost %
Results
Live estimates based on your inputs and editable fee assumptions.
Recommended safety stock
195
Buffer units to hold.
Safety stock value
$1,560.00
Dollar value tied in buffer.
Annual holding cost
$390.00
Cost to carry safety stock yearly.
Days buffer at avg demand
13
Safety stock divided by avg daily.
Days buffer at max demand
7.80
Safety stock divided by max daily.
Service level chosen
95
Target in-stock rate.
What this means
195 units safety from (25×12 − 15×7) = 300−105. $1560 tied, $390/yr holding. 13.0 days at avg, 7.8 days at max. 95% service (z=1.65).
Safety stock at different service levels
Interactive breakdown of fees, costs, and remaining profit.
Distribution
- 90%$151.2717.9%
- 95%$195.0023.1%
- 97%$222.1826.3%
- 99%$275.3632.6%
Total $843.82 · 4 segments · interactive
Line-item breakdown
Dollar amounts, share of revenue, and visual proportion.
- Avg demand during lead time
- 105
- Max demand during max lead
- 300
- Recommended safety stock
- 195
- Safety stock value
- $1,560.00
- Annual holding cost
- $390.00
- Days at avg demand
- 13
- Days at max demand
- 7.80
- At 90% service level
- 151.27
- At 99% service level
- 275.36
Assumptions used
- • Max 25×12=300 minus avg 15×7=105 = 195 safety
- • $8.00 × 195 = $1560.00
- • Holding 25% × $1560.00 = $390.00/yr
Share or export this calculation
Copy your numbers, save as PDF, or share with your team and seller communities.
Continue with related tools
These calculators pair well with Safety Stock and help you get a complete picture.
You might also need
Reorder Point
Find the exact inventory level to place a new order — balance stockouts against carrying costs using lead time demand plus safety stock.
You might also need
EOQ
Find your optimal order quantity — the sweet spot that minimizes total inventory costs including ordering and holding.
Stock smarter
Inventory
Calculate reorder point, safety stock, economic order quantity, and carrying costs for your inventory.
📈Grow Your Business with Smart Sellers Tool
Want more than just the numbers?
Download the FREE Smart Seller Profit Toolkit and learn how to:
Get your free toolkit and start pricing smarter today.
Get the Free ToolkitFree • No spam • Unsubscribe anytime
Safety Stock Calculator
Generated 8/4/2026, 2:51:03 PM · Currency USD
Inputs
- Average daily demand: 15
- Max daily demand: 25
- Average lead time (days): 7
- Max lead time (days): 12
- Service level target: 95
- Cost per unit: 8
- Annual holding cost %: 25
Results
- Avg demand during lead time: 105
- Max demand during max lead: 300
- Recommended safety stock: 195
- Safety stock value: $1,560.00
- Annual holding cost: $390.00
- Days at avg demand: 13
- Days at max demand: 7.80
- At 90% service level: 151.27
- At 99% service level: 275.36
Interpretation
195 units safety from (25×12 − 15×7) = 300−105. $1560 tied, $390/yr holding. 13.0 days at avg, 7.8 days at max. 95% service (z=1.65).
How it works
Methodology & formulas
This calculator is transparent by design. Review the steps and formulas so you can trust the estimate and adjust assumptions when your dashboard differs.
Calculation steps
- 1Calculate average demand during lead time as avgDaily × avgLead.
- 2Calculate max demand during max lead as maxDaily × maxLead.
- 3Basic safety is difference between max scenario and average scenario.
- 4Value days of buffer at both average and peak rates.
- 5Show how safety scales with 90/95/97/99 service levels using ratio to 95% base.
Formulas
- avgLeadDemand = avgDaily × avgLead
- maxLeadDemand = maxDaily × maxLead
- safetyBasic = maxLeadDemand − avgLeadDemand
- safetyValue = safety × unitCost
- holdingAnnual = safetyValue × holding%/100
- bufferDays = safety / dailyRate
Important assumptions
- Basic safety stock = (maxDaily × maxLead) − (avgDaily × avgLead).
- Z-scores: 90%=1.28, 95%=1.65, 97%=1.88, 99%=2.33.
- Safety value = safety units × unitCost.
- Annual holding cost = safety value × holdingCost%.
- Buffer days = safety units / daily demand rate.
Worked example
Average 15/day, max 25/day, 7 vs 12 day lead
Avg 15/day × 7 days =105 avg lead demand. Max 25/day ×12=300 max demand. Basic safety 195 units. At $8 = $1,560 value, $390 holding yearly at 25%. At 15/day =13 days buffer, at 25/day=7.8 days. 90% =161 units, 95%=195, 99%=234.
FAQ
Common questions
Related tools
Continue planning
Reorder Point Calculator
Find the exact inventory level to place a new order — balance stockouts against carrying costs using lead time demand plus safety stock.
Economic Order Quantity Calculator
Find your optimal order quantity — the sweet spot that minimizes total inventory costs including ordering and holding.
Inventory Calculator
Calculate reorder point, safety stock, economic order quantity, and carrying costs for your inventory.
Platform roadmap
Explore More Seller Tools
We are building a complete business decision platform. These planning and forecasting tools are coming next — each will reuse the same transparent, seller-focused framework.
Profit Planner
Set monthly income goals and work backward to required sales, pricing, and margin targets.
Inventory Planner
Calculate reorder points, inventory investment, and stockout risk before you place POs.
Pricing Optimizer
Test pricing scenarios to find the sweet spot between conversion and profit per order.
ROI Planner
Model return on ads, influencer campaigns, and marketplace promotions.
Business Goal Planner
Turn annual revenue goals into daily sales targets, listing counts, and traffic needs.
Sales Forecast
Project next quarter revenue from current average order value and growth assumptions.
Pricing Strategy Tool
Compare charm pricing, premium pricing, and anchor strategies on the same product.
Product Launch Calculator
Budget a new product launch including samples, fees, ads, and break-even timeline.