NodusTechInventory Reorder Point Calculator
Enter your average and maximum daily usage and supplier lead time to get a safety stock figure and the exact reorder point.
How to read your result
Safety stockis the buffer that absorbs a worse-than-average week — either you sell faster than usual, or your supplier takes longer than usual to deliver. It's the gap between demand in your worst realistic case and demand in your average case, both measured over the relevant lead time.
The reorder pointis your average demand during lead time plus that safety stock. Order as soon as stock on hand reaches this number — not when you're already out.
Worked example
A shop sells 20 units/day on average (peaking at 35 units/day) and its supplier usually delivers in 5 days (worst case 8 days). Safety stock = (35 × 8) − (20 × 5) = 280 − 100 = 180 units. Average demand during lead time = 20 × 5 = 100 units. Reorder point = 100 + 180 = 280 units — as soon as stock drops to 280 units, it's time to order again.
Formula
Safety stock = (Max daily usage × Max lead time) − (Average daily usage × Average lead time)
Reorder point = (Average daily usage × Average lead time) + Safety stock
Good to know
This is the standard, widely used reorder-point formula from inventory management — it works well once you have a few months of real sales and delivery data to estimate averages and worst cases from. For products with very irregular or seasonal demand, revisit these numbers regularly rather than setting them once.
Frequently Asked Questions
What is a reorder point?+
The stock level that should trigger a new purchase order. Once stock on hand drops to the reorder point, you order more — timed so the new stock should arrive around when you'd otherwise run out.
Why does it need a "maximum" usage and lead time, not just an average?+
Averages describe a typical week, not your worst week. Safety stock is sized from the gap between your worst realistic case (max usage × max lead time) and your average case — that gap is what protects you from a stockout when demand spikes or a delivery runs late.
What if I don't know my maximum daily usage or lead time?+
Use your highest realistic figure from the last few months rather than an extreme one-off. If you're unsure, start with your average plus 20–30% as a rough estimate and refine it as you collect real data.
Does this calculate how much to order, not just when?+
No — this calculator answers only "when to reorder" (the reorder point). Order quantity is a separate decision that depends on supplier minimums, storage space and cost, typically handled alongside a fuller inventory system.
Need this running automatically across your whole product catalogue?
Business Inventory & Stock Control Toolkit — €19.99
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This calculator is provided for general information only and is not accounting, tax or financial advice.