Formula
Invites accepted / Invites sent x 100
How to measure
Track every invite sent through the in-product invite mechanic and divide accepted invites by total invites sent.
Why track it
This rate isolates the quality of the invite mechanic and messaging itself, separate from how many invites get sent in the first place.
Example
A collaboration tool improves invite acceptance from 20% to 38% by redesigning the invite email's preview and call to action.