IFERROR() – Returns a value if an expression errors, otherwise returns the expression's result

IFERROR(value, replacement)

• value: The argument to check for an error. This can be a cell reference, a formula, or an expression (e.g., T1A1/T1B1).
• replacement: The value to return if the value argument evaluates to an error. This can be text, a number, a blank string (""), or another formula.

IFERROR(T1A1/T1B1, "Error in calculation")

This example attempts to divide the value in cell T1A1 by the value in cell T1B1.

• If T1B1 contains 0 (which would cause a division by zero error), the function returns "Error in calculation".
• If T1A1 = 10 and T1B1 = 2, the division 10/2 results in 5 (no error), so the function returns 5.

• Error trapping: Provides a way to gracefully handle errors that might otherwise stop calculations or display unhelpful error messages.
• Custom error messages: Allows you to display user-friendly messages or alternative values instead of standard error codes.
• Fallback values/calculations: The replacement can be a static value or another calculation to perform if the primary one fails (e.g., IFERROR(T1A1/T1B1, 0) to return 0 on error).

• Preventing division by zero errors in calculations: IFERROR(SUM(T1A1:T1A5)/COUNT(T1A1:T1A5), "Cannot calculate average").
• Displaying "N/A" or "Invalid input" if a formula relies on user input that could be problematic.
• Substituting a default value, like 0, when an error occurs in a calculation: IFERROR(T1A1/T1B1, 0).

• Text replacement not in quotes: If the replacement value is text, it must be enclosed in double quotes.
• Masking all errors: While useful, IFERROR() can sometimes hide underlying problems in your data or formulas if used too broadly without understanding the cause of potential errors.
• Incorrect argument order: Ensure the value/expression to check is first, followed by the replacement value.