Free Tool by VNDLY
Safety Stock Calculator
Find the right buffer stock to absorb demand spikes and late deliveries. Enter your average and maximum usage and lead time to get your safety stock instantly.
Your safety stock
610
units — buffer for demand spikes and supplier delays
Lead-time demand
350
avg usage × avg lead time
Max demand during lead time
960
max usage × max lead time
Typical units sold or consumed per day.
Your busiest realistic day.
Usual days from ordering to receiving stock.
The longest a restock has realistically taken.
The formula
Safety stock = (max daily usage × max lead time) − (avg daily usage × avg lead time)
100% free · no signup · calculated in your browser.
Stop guessing your safety stock
This calculator gives you a static safety stock number. Real inventory needs dynamic safety stock — one that adjusts as your demand patterns shift. VNDLY tracks every SKU's actual sales velocity and supplier lead times, then automatically recalculates safety stock and reorder points in real time.
How to use this calculator
1. Enter average daily usage
Typical units sold or consumed per day.
2. Enter maximum daily usage
Your busiest realistic day.
3. Enter average lead time
Usual days from ordering to receiving stock.
4. Enter maximum lead time
The longest a restock has realistically taken.
Why safety stock matters
Safety stock is the cushion between your average demand and worst-case demand. It protects you from stockouts when sales spike or a supplier is late — but too much ties up cash and warehouse space.
Lead-time demand
Average daily usage × average lead time. The baseline stock you'll need while waiting for a delivery.
Max demand during lead time
Maximum daily usage × maximum lead time. The worst-case demand you need to survive.
Safety stock
The difference between max demand during lead time and lead-time demand.
Reorder point
Lead-time demand + safety stock. The stock level that triggers a new order.
From a static buffer to dynamic safety stock
This calculator gives you a static safety stock number. Real inventory needs dynamic safety stock — one that adjusts as your demand patterns shift. VNDLY tracks every SKU's actual sales velocity and supplier lead times, then automatically recalculates safety stock and reorder points in real time. Starting at $49/mo.
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Frequently asked questions
What is safety stock?
Buffer inventory held to protect against demand spikes and supplier delays.
What is the safety stock formula?
(Max daily usage × max lead time) − (avg daily usage × avg lead time).
How much safety stock is too much?
Safety stock has a cost: storage, cash tied up, risk of obsolescence. The right level balances stockout risk against holding cost. Start here, then refine with real demand variability data.
What's the difference between safety stock and reorder point?
Safety stock is a buffer (how much extra to hold). Reorder point is the trigger (when to order). Reorder point = lead-time demand + safety stock.
Does this formula work for seasonal products?
No — the classic formula assumes steady demand. For seasonal SKUs you need software that forecasts from real sales history, like VNDLY.