T30D (Trailing 30 Days) - Amazon Glossary

T30D is a rolling time-window metric representing the Trailing 30 Days of performance data. Amazon sellers and vendors use this specific lookback period to analyze recent trends in sales velocity, advertising efficiency, and inventory health, providing a more stable dataset than daily or weekly snapshots.

Why Does T30D Matter?

T30D is the "gold standard" for balancing responsiveness with statistical significance. It filters out the "noise" of weekend dips or mid-week spikes, allowing a seller to assess if their profitability and ACoS are trending toward long-term goals. Relying on T30D prevents knee-jerk reactions to single-day fluctuations that could disrupt a successful strategy.

How is T30D Calculated?

To calculate any T30D metric, you aggregate the data from the last 30 completed days, excluding the current day (to account for data lag).

$$Metric_{T30D} = \sum_{t=d-30}^{d-1} Value_{t}$$

For example, to find your T30D Sales Velocity:

$$Velocity_{T30D} = \frac{Total\ Units\ Sold\ (Last\ 30\ Days)}{30}$$

T30D in Practice

A seller tracking a new supplement launch notices that sales on Tuesday were 50% lower than Monday.

• Correct Approach: The seller looks at the T30D trend line. They see that despite the Tuesday dip, the 30-day average has increased by 15% month-over-month. They maintain their current Ad Spend because the macro-trend is healthy.

• Common Mistake: The seller panics over the single-day "cliff," slashes their bids, and kills the momentum of their Rank Tracker progress right before a high-traffic weekend.

FBA vs. FBM Context

In the context of Fulfillment by Amazon (FBA), T30D is crucial for calculating Aged Inventory surcharges and restock limits. Amazon's internal algorithms use your T30D sales volume to determine how much space you are allocated at a fulfillment center. For Fulfillment by Merchant (FBM), T30D is primarily used to monitor shipping performance metrics like the Late Shipment Rate.

Why Use T30D Over Other Windows?

How does T30D compare to T7D?

While T7D (Trailing 7 Days) shows immediate impact, it is often skewed by external factors like paydays or holidays. T30D provides the conversion data needed for Amazon's A9 algorithm to "settle," as some customers may click an ad today but not purchase for several days.

Is T30D better for inventory planning?

Yes. For most standard-lead-time products, T30D offers a reliable forecast of future demand. It helps avoid stockouts by providing a smoothed average of daily units sold, which is essential for setting accurate reorder points.

SoldScope Expert Tip

When analyzing T30D advertising data, always cross-reference it with your TACoS (Total Advertising Cost of Sale). A stable T30D ACoS is good, but if your organic sales are dropping during that same window, your dependency on ads is increasing. Use the T30D window to spot "bleeding" campaigns that look efficient on a 7-day view but fail to contribute to overall account growth over a full month.

FAQ

How to see T30D sales in Seller Central?

Go to the 'Reports' tab, select 'Business Reports,' and then 'Sales and Traffic.' In the date range selector, choose the 'Last 30 Days' option to see your aggregated T30D performance.

Does T30D include today’s data?

Typically, no. In professional reporting, T30D refers to the last 30 completed days. Because Amazon's Attributed Sales can take up to 48–72 hours to fully clear, including today or yesterday often results in artificially deflated metrics.

Why is my T30D ACoS different from my Lifetime ACoS?

T30D reflects your most recent campaign optimizations and current market competition. Lifetime ACoS includes data from when your listing may have been unoptimized or during high-traffic events like Prime Day, making it less useful for day-to-day management.