Assortment depth
Assortment depth is the number of options a store offers inside one product category: models, sizes, colours and price tiers.
How it works
Depth measures choice inside a category: a shop with 40 kinds of mug is deeper in mugs than one with five. Its counterpart is assortment breadth, the number of categories. Models, sizes, colours and price tiers all add depth.
Going deeper adds products to a category that already has buyers and a sales history in the ad account. To choose which way to expand, read assortment breadth vs depth.
Formula
Products in one category; store average = products ÷ categories
Ways to calculate
- Products in a line — the textbook “product line depth” (OpenStax, Principles of Marketing).
- Variations of each product — Wikipedia’s “Product lining” counts depth this way and calls the total number of products “length”.
- Feed items — each size or colour is a separate item, linked to the others by
item_group_id(Merchant API, ProductAttributes), so the count is higher than by model.
Example
Example store, not client data.
The tableware shop has 3,000 products in 12 categories: average depth 3,000 ÷ 12 = 250. Its mug category holds 100 models in four colours each. Counted by model, mug depth is 100; counted by feed item, 100 × 4 = 400.
Not to be confused with
- SKU — one item you can ship on its own. Depth counts SKUs, or models, within a category.
- Product variants — sizes and colours of one model. They add to depth only when you count by item.
Right and wrong readings
- Wrong: “Mug depth grew from 100 to 400 after we loaded the colours into the feed.” Right: only the way of counting changed; by model it is still 100.
- Wrong: “Going deeper is safe, going broader is a gamble.” Right: in GetProfit data (June 2025 – June 2026), 4.0% of new products in categories that already sold made a sale within three months. In categories without earlier sales, 3.5% did. Store by store, the categories that already sold did better in only 51 of the 83 stores compared.
Sources
- 9.2 Product Items, Product Lines, and Product Mixes — OpenStax: product line depth. Checked 2 October 2026.
- Product lining — Wikipedia: width, length and depth of a product mix. Checked 2 October 2026.
- ProductAttributes — Merchant API: the shared identifier for variants of one product. Checked 2 October 2026.
- GetProfit data: 696,921 new products in categories with earlier sales and 63,921 without, June 2025 – June 2026 — the share that sold within three months.