Net Dollar Retention (NDR), sometimes used interchangeably with NRR, measures how much recurring revenue is retained and grown from the existing customer base over a given period. An NDR above 100% indicates that expansion revenue outpaces churn and downgrades.

Example: Starting with $1,000,000 ARR from existing customers, gaining $150,000 from expansions, and losing $80,000 from churn gives an NDR of 107%.