Attach rate

The share of bookings that also buy a particular extra. If 100 guests book and 12 of them add travel insurance, the attach rate on insurance is 12%.

It is the number to watch on any upsell, because revenue per sale tells you nothing on its own. A €40 add-on with a 3% attach rate earns less than a €6 one at 30%.

Attach rates depend heavily on where the offer appears. An extra presented inside the booking flow, while the guest is already paying, typically converts several times better than the same extra emailed a week later. The same holds for the channel: an item offered at the front desk at check-in and an item sitting in a pre-arrival message are not comparable, even at the same price.

Useful benchmarks are internal rather than industry-wide. Measure your own attach rate per offer and per placement, change one thing at a time, and compare against the version before it.