How does Roll-Up Summary Field work in Salesforce?
Roll-up summary fields are available only on the master side of a master-detail relationship. They calculate aggregate values across all related detail records, or a filtered subset based on criteria you define. For example, a roll-up on the Account object could SUM the Amount field across all closed-won Opportunities, or COUNT the number of open Cases. The aggregated value is stored on the parent record and recalculated whenever detail records are created, updated, deleted, or undeleted.
Each object supports up to 25 roll-up summary fields. Filter criteria on roll-up summaries let you narrow the calculation to specific records (e.g., only Opportunities where Stage equals 'Closed Won'). Because roll-ups require master-detail relationships, they are not available across lookup relationships by default; for those scenarios, admins use declarative tools like Flow (with triggered paths) or third-party AppExchange solutions like Declarative Lookup Rollup Summaries (DLRS). Clientell AI can identify where roll-up summaries would eliminate manual calculations in your org and configure them automatically.