Items per order
Items per order (average basket size) is the total quantity of units sold divided by the number of orders over a period. It describes how many items a typical order contains, independent of price. Together with average order value it decomposes revenue per order into quantity and price effects, which is why merchandising and bundling work is often judged on basket size rather than value alone.
What this means
Items per order sums the quantity across all order line items and divides by the order count. GA4's purchase event carries an items array with per-item quantity, so the unit total is collectable. The metric is purely about basket size: a $100 order of ten items and a $100 order of one item are identical in average order value but very different in items per order.
Why decompose revenue this way
Revenue per order equals average order value, and that value is the product of basket size and average item price. Splitting it into items per order and price-per-item tells you which lever is moving. Cross-sell modules, free-shipping thresholds, and bundles are designed to lift basket size, so judging them on items per order — not just total revenue — isolates whether they worked.
Watch for refunds and cancellations: net them consistently so the unit and order counts align.
- Total units sold ÷ number of orders
- Independent of item price (basket size only)
- Pairs with AOV to split quantity from price effects
How it appears in analytics and logs
A rising items-per-order with flat average order value means baskets are growing on cheaper items; a flat basket with rising value means price or mix shifted upward. Reading the two together separates quantity effects from price effects.
Diagnostic use case
Track basket size to evaluate cross-sell, bundling, and minimum-order incentives separately from price-driven changes in order value.
What WebmasterID can help detect
WebmasterID records purchase events with item arrays first-party, so units per order are derived without third-party cart cookies, and bot orders can be excluded from the order count.
Common mistakes
- Confusing basket size with average order value.
- Counting orders and units over mismatched windows or refund rules.
- Crediting a value lift to basket growth without checking price mix.
Privacy and accuracy notes
Items per order is an aggregate ratio of units to orders. It needs no personal data; item quantities come from order line items, not buyer identity.
Related pages
- Conversion value
Conversion value is the monetary worth attached to a conversion or key event. In GA4 it comes from the value parameter (with currency) sent on events such as purchase or generate_lead, and it feeds revenue, ROAS, and page-value calculations. Because it is whatever you assign — a real order total or an estimated lead worth — its reliability depends entirely on consistent, correctly scoped tagging.
- Average order value (AOV)
Average order value (AOV) is total revenue divided by the number of orders. It is simple but easy to misread: a few large orders pull the mean upward, refunds and taxes change what 'revenue' means, and mixing currencies without conversion corrupts it. For skewed order sizes, the median order value is often more honest.
- The purchase event and e-commerce
The purchase event records a completed transaction and anchors all e-commerce reporting: revenue, items, and conversion value. It carries a transaction id, a value and currency, and an items array describing what was bought. The discipline is to record the order, not the customer — product and revenue data belong in the event, personal identity does not.
- Event Explorer
Inspect item arrays inside purchase events.
Sources and verification notes
- Google — GA4 purchase event items arrayDocuments per-item quantity used to total units per order.
Last reviewed 2026-06-24. Facts are checked against primary/official sources where available; uncertain specifics are marked “Data not yet verified” rather than guessed.