Formula fields

Formula fields are saved expressions that compute a value from a task, a project or a goal, such as days until due, a flag for overdue and high priority, or a score from the estimate. You write the expression as text in the style of a spreadsheet, check it against a sample row as you type, and save it with a name, a scope and the type of value it returns. A formula only reads: it never changes the record. You preview a formula on a sample record in Settings and evaluate it through the API and the assistant tools; saved views, boards and reports do not read it.

• Write the expression as text, with live parse errors, a list of built-in functions and example expressions; an advanced mode accepts the expression as raw JSON
• Choose whether the formula reads tasks, projects or goals, and whether it returns yes or no, a number, text or a date
• Evaluate a saved formula over up to 500 rows in one API call

• Formulas are pure, with no side effects and no external calls.
• One evaluation call accepts at most 500 rows. Send larger sets in several calls.

1. 1Open Settings, then Formula fields, and choose Start a new formula.
2. 2Choose the scope and the return type, name the formula, and type the expression. The result previews live against a sample row.
3. 3Try a formula against a sample row in Settings, then Formula fields, before you save it. The same screen lists the formulas you have saved.

Can a formula field write back to the record?

No. Formula fields are read-only and pure: no side effects and no external calls. They compute a value from the record, and the underlying fields are unchanged.

Is there a limit to how many rows I can evaluate?

Yes. One call to the evaluate endpoint accepts at most 500 rows. The cost also grows with the number of rows multiplied by the size of the expression, so run one formula over many rows in a single call rather than one call per row, and split anything above 500 rows into several calls.

Can I use a formula field as a column in a view, a board or a report?

No. Saved views, boards and reports do not read saved formulas. A saved formula is previewed on a sample record on the Formula fields screen, and evaluated through the API and the assistant tools against rows you send. The Views screen applies one built-in rule that tints overdue high-priority tasks, and it does not read your formulas.