Quick answer
You can create up to 40 lookup relationship (LR) fields on a single Salesforce object. This limit applies to lookup relationship fields (custom) and is separate from the number of master-detail relationships.
Explanation
Salesforce enforces different limits for relationship types. The key limits to remember are:
- Lookup relationships per object: 40
- Master-detail relationships per object: 2
Lookup relationships allow one object to reference another (one-to-many), while master-detail creates a tighter parent-child relationship with cascade deletes and roll-up summary features. Because master-detail relationships have stronger implications for sharing, security, and data integrity, their count is restricted to a smaller number.
Why this matters
Hitting the lookup limit can block new integrations or data model changes. If your data model requires more relationships than allowed, consider these alternatives:
- Use a junction object (many-to-many) to model multiple relationships without adding many lookup fields to the same object.
- Consolidate references into a single relationship and store additional reference info in a related child object.
- Use external IDs or a composite key approach when integrating external systems, reducing the need for multiple lookup fields.
Practical tips
- Plan your data model early. Map out objects and relationships to avoid hitting the limit in production.
- Favor normalized designs (junction objects) over adding many lookup fields to a single object.
- Use formula fields and indexed fields carefully; excessive cross-object formulas can affect performance when many lookups exist.
- Review managed package objects: some limits can be impacted by package-specific relationships depending on namespace and packaging.
Example SOQL referencing a lookup
SELECT Id, Name, Account__r.Name, Contact__r.Email FROM Custom_Object__c WHERE Account__r.Industry = 'Technology'
This demonstrates how to traverse lookup relationships in SOQL using the relationship name (Account__r, Contact__r) to access parent fields.
References
Always check the latest Salesforce Limits documentation as limits can change between releases. The above numbers are commonly quoted limits in Salesforce editions for custom objects.