Free Inventory Forecast & Reorder Point Calculator UK (2026)
Written by Calvin Lo, Founder of Aphelios Software | July 2026 | 5 min read
Accurately predict stockouts, calculate reorder points, and optimise inventory decisions using demand trends, lead time, and safety stock modelling.
Built for UK retailers, eCommerce businesses, wholesalers, and inventory managers.
Inventory Forecasting Tool
Estimated Days Until Stockout
0
Recommended Reorder Quantity
0
How This Inventory Forecast Calculator Works
This tool uses a demand-based forecasting model to estimate future stock depletion. It adjusts daily sales using trend data, then calculates how long current inventory will last and when you should reorder.
Combine forecasting with Inventory Management Software for real-time stock visibility and automated purchasing.
Inventory Forecasting Formula Explained
The calculator adjusts average daily sales based on trend percentage, then applies lead time and safety stock to determine reorder requirements.
- Adjusted Demand = Daily Sales × (1 + Trend)
- Lead Time Demand = Adjusted Demand × Lead Time
- Safety Stock = Lead Time Demand × Safety Percentage
- Reorder Point = Lead Time Demand + Safety Stock
Real-World Example
A UK retailer selling 20 units per day with 7-day supplier lead time and increasing demand (+10%) would need to reorder before stock drops below critical levels. This prevents lost sales and improves cash flow planning.
Who Should Use This Tool?
- UK retail stores managing physical inventory
- eCommerce businesses forecasting demand
- Wholesale distributors managing bulk stock
- Supply chain and procurement teams
Common Inventory Mistakes
- Ignoring seasonal demand changes
- Not updating sales trends regularly
- Underestimating supplier lead times
- Failing to maintain safety stock buffers
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Stock Forecast Calculator FAQ
What is a stock forecast calculator?
A stock forecast calculator predicts future inventory levels based on sales trends, lead time, and stock levels. It tells you when to reorder and how much to order to avoid running out.
How is reorder point calculated?
Reorder point is calculated using demand during lead time plus safety stock. It is the stock level at which you should place a new order to prevent stockouts before the next delivery arrives.
Who should use this inventory tool?
Retailers, wholesalers, eCommerce sellers, and supply chain operators use the calculator to optimise inventory levels, plan purchases, and improve cash flow.
Why is safety stock important?
Safety stock protects against unexpected demand spikes or supplier delays. It keeps stock available during peak periods when sales are higher than forecast.
How can I reduce stockouts?
Set accurate reorder points, review sales trends regularly, maintain safety stock, and automate purchasing so stock is replenished before it runs out. Inventory software can trigger reorder alerts automatically.
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