Metrics & KPIs
Attach Rate
The percentage of orders that include a secondary item — typically an upsell, bundle, or order bump. Every 10% of attach rate is ~4-6% of AOV lift.
Attach rate is the percentage of orders that contain at least one secondary item beyond the main product — an order bump at checkout, a bundled accessory, or a post-purchase upsell. It's the operational metric behind AOV growth.
Every 10% increase in attach rate typically lifts AOV by 4-6%, which compounds directly into contribution margin (because the attached item usually has similar or better margin than the hero product, and there's no additional CAC).
The two highest-leverage attach-rate plays:
- Pre-purchase order bump: A single checkbox on the checkout page — "Add this accessory for $X more."
- Post-purchase one-click upsell: An additional offer on the thank-you page that bypasses re-entering payment info.
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