About

About Inventory Buffer Calculator

Free, browser-based planning tools and worked-example guides for planners at small and mid-sized manufacturers and distributors.

Updated October 16, 2026

What's here

Calculators for DDMRP-style buffer zones, safety stock, reorder points, EOQ and ABC/XYZ classification. Each one shows its formulas with your numbers.
A planning workspace that keeps your item master, stock, open orders and usage in your browser and lists what to order today, most urgent first.
Guides with worked examples and a glossary of the terms they use.

How the numbers are checked

Every worked example in the guides is recomputed in code before it is published, and the planner's math is covered by automated tests that use the same examples.
Each formula is written out next to its result, so you can check any number yourself.
Assumptions and limits are stated where they matter, for example what a service level does and doesn't mean.
Found an error? Corrections are welcome and pages show the date they were last updated.

Your data

The calculators and the planner run in your browser. Numbers you type and files you import are processed on your device and are not uploaded. The planner saves its workspace in your browser's own storage. There are no ads, sign-ups or third-party trackers; the site host keeps standard anonymous visit counts.

Independence

This site isn't affiliated with or endorsed by the Demand Driven Institute or any software vendor. "DDMRP" describes the publicly documented method. Results are decision support: review them before acting.

Paid help

If you'd rather have the analysis done for all your items, a fixed-price inventory health and safety-stock checkup is available through Upwork. It is produced with AI tools and automated scripts, with a separate automated check pass, then reviewed and signed off by a CPIM- and DDMRP-certified planner. See a sample report or the tiers on Upwork.

Want the full picture for all your SKUs?

A fixed-price inventory health and safety-stock checkup: send one export and get a workbook with ABC/XYZ classes, excess and no-movement inventory, safety stock and reorder points, plus buffer screening in the Advanced tier. The analysis is AI-assisted and reviewed and signed off by a CPIM- and DDMRP-certified planner. Ordered and paid through Upwork.