Demand Forecasting

Demand forecasting is the analytical process of estimating how many units of a product will be sold in a future time period — typically the next 30, 60, or 90 days. Accurate forecasting is the foundation of inventory management: it determines how much to order, when to reorder, and how much safety stock to carry.

Why Demand Forecasting Is Critical for FBA Sellers

Two equally costly mistakes arise from poor forecasting:

• Underestimate demand → stockout — lose organic ranking, miss sales, potentially face long restock timelines
• Overestimate demand → overstock — accumulate monthly storage fees, long-term storage surcharges, and capital tied up in unsellable inventory (lowering IPI score)

The goal of forecasting is to stay in the narrow channel between these two failure modes.

Forecasting Methods

Moving Average

Average sales over the last N weeks/months. Simple and effective for stable, low-seasonality products.

Forecast = Average of last 8 weeks of sales

Weighted Moving Average

Assigns higher weight to recent periods. Better for products with growing or declining trends.

Forecast = (0.5 × Week −1) + (0.3 × Week −2) + (0.2 × Week −3)

Year-over-Year with Seasonal Adjustment

Best for products with predictable seasonality (holiday demand, summer spikes).

Forecast = Last Year's Same-Period Sales × Current Year Growth Rate × Seasonal Index

Machine Learning (for advanced sellers)

Regression models or neural networks that incorporate external variables — weather, competitor pricing, search trend data, promotion calendars. These require significant data volume and technical investment.

Inputs That Improve Forecast Accuracy

• Historical sales velocity (minimum 6–12 months)
• Seasonality index (compare same week year-over-year)
• Planned promotions — Prime Day, Lightning Deals, coupons add spike demand
• Competitor activity — if a major competitor goes out of stock, your velocity jumps
• Ad spend changes — doubling PPC budget can materially shift velocity

Forecasting vs. Amazon's Restock Recommendations

Amazon provides restock recommendations in Seller Central based on your sales velocity and IPI score, but these recommendations optimize for Amazon's fulfillment network capacity, not your margin. They sometimes recommend overstocking to avoid any FC throughput risk. Use Amazon's numbers as a check, not a directive.