If you’ve ever looked at your DMS-reported fill rate or inventory turns and thought, “This doesn’t feel right”—you’re not alone.

In this month’s webinar, Chuck Hartle broke down the most common flaws in how DMS platforms calculate fill rates and turn rates—and shared how Parts Managers can take back control with simple, real-world math.

Why Most DMS Fill Rate & Turn Reports Are Misleading

Fill rate might show 90% on paper, but that doesn’t mean your techs aren't waiting on parts. Chuck explained how most DMS systems track same-day fill or manipulate data based on how parts are receipted—giving a false sense of inventory performance.

On the flip side, True Turns—used in CDK and other systems—are based on outdated practices from the 1980s when stock orders still came with incentives. In today’s world of daily replenishment and ASR programs, Gross Turns are the more meaningful metric.

“If you're relying on your DMS to calculate true inventory performance, you’re likely getting a distorted view.”

How to Calculate Real Turns and Day Supply (No Matter Your DMS)

Chuck walked through a simple formula to get clarity:

• Gross Turns = (Net Sales at Cost × 12) ÷ Inventory Value

• Day Supply = (Inventory ÷ Monthly Sales) × 30

He then showed how to find those numbers inside six major DMS systems—CDK, Reynolds, Dealertrack, Tekion, PBS, and Automate—along with examples and pitfalls to avoid.

⚠️ Red Flags to Watch

• Same-day fill rates that look great but don't reflect off-the-shelf availability

• Tech complaints about delays on common parts

• High days supply or low turns despite strong sales

• ASR-controlled parts constantly running out or aging out

Chuck reminded us that inventory should be working, not sitting. A healthy inventory typically falls between 6–8 gross turns and a 45–55 day supply, depending on business type.

Practical Takeaways

• Don’t blindly trust DMS fill rate or turn reports

• Calculate your own using actual sales and inventory values

• Watch for overstock on maintenance items post-ASR panic buys

• Use your sources and reports to track actual stock movement and adjust strategy

• Build inventory breadth to support technicians and boost CSI

“Your inventory is an investment. It's either generating revenue—or gathering dust.”