Supply Chain Calculators
Inventory Calculators
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EOQ, safety stock, reorder point, lead time, inventory turnover, and days of supply — instant results with every formula explained. No account needed.
Built by our team of supply chain professionals — people who use these formulas on the job every day, not content writers filling a brief.
We've worked in procurement, demand planning, and inventory management across manufacturing, retail, and e-commerce — these are the tools we reach for daily.
Every formula is cross-referenced against APICS and CSCMP standards and tested against real inventory data before it goes live.
Every calculator shows the formula, defines each variable, and walks through a worked example — so you understand the result, not just receive it.
No signup, no paywall, no upsell. Every calculator and guide on this site is free to use, forever.
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How much should I order?
Find the order quantity that minimises your total inventory costs — balancing ordering and holding costs.
How much buffer do I need?
Calculate the buffer inventory that protects your service level against demand variability and lead time fluctuations.
When should I reorder?
Get the exact stock level at which to place your next order, including safety stock coverage.
How long does replenishment take?
Break down total lead time across processing, production, and transit — and see how it flows into your reorder point.
What is my turnover ratio?
Full turnover analysis including Days Inventory Outstanding (DIO), COGS-based and revenue-based methods.
How long will my stock last?
See how many days your current inventory will cover, with lead time coverage indicator and stockout date.
Process
Go from question to answer in three steps — no account, no setup, no waiting.
Pick the tool that matches your question — order quantity, reorder timing, buffer stock, lead time, or turnover.
Fill in demand, costs, and lead times. Every field has inline hints so you always know exactly what to enter.
Results appear instantly with a full formula breakdown — so you understand the number, not just receive it.
Not sure which formula to use? Every guide explains the theory, walks through a worked example, and links to the matching calculator.
EOQ
Learn why EOQ is the foundation of replenishment planning and how it minimises your total inventory cost.
Read guide →Safety Stock
Understand how buffer inventory protects your service level against demand spikes and supplier delays.
Read guide →Reorder Point
The stock level that triggers your next purchase order — and why getting it right prevents stockouts.
Read guide →Lead Time
A breakdown of every component that makes up total lead time — and how it flows into reorder point.
Read guide →EOQ
The complete formula with every variable defined, a worked example, and common calculation mistakes.
Read guide →Safety Stock
Four safety stock methods compared — from the basic average to the service-level statistical approach.
Read guide →Inventory Turnover
How to calculate turnover ratio, what it tells you about efficiency, and how to benchmark your result.
Read guide →Days of Supply
Days of supply explained: formula, worked example, and how to use it as your daily replenishment signal.
Read guide →