How to Use ISNUMBER in Excel: Simple Guide and Examples

Use the ISNUMBER function in Excel to check if a cell contains a numeric value. It returns TRUE if the cell has a number and FALSE if it does not. This helps you test data before calculations or filtering.

Syntax

The ISNUMBER function has a simple syntax:

• value: The cell or expression you want to check if it is a number.

It returns TRUE if value is a number, otherwise FALSE.

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ISNUMBER(value)

Example

This example shows how ISNUMBER works with different cell values:

• If A1 contains 123, =ISNUMBER(A1) returns TRUE.
• If A2 contains "Hello", =ISNUMBER(A2) returns FALSE.
• If A3 contains a formula result like =5+3, =ISNUMBER(A3) returns TRUE.

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A1: 123
A2: Hello
A3: =5+3

B1: =ISNUMBER(A1)
B2: =ISNUMBER(A2)
B3: =ISNUMBER(A3)

Output

B1: TRUE
B2: FALSE
B3: TRUE

Common Pitfalls

Common mistakes when using ISNUMBER include:

• Checking cells with numbers stored as text returns FALSE. For example, "123" as text is not a number.
• Using ISNUMBER on empty cells returns FALSE.
• Confusing ISNUMBER with functions that check for errors or blanks.

To fix text numbers, convert them using VALUE or multiply by 1.

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Wrong: =ISNUMBER("123")  // returns FALSE because "123" is text
Right: =ISNUMBER(VALUE("123"))  // returns TRUE after conversion

Quick Reference

Usage	Description	Example
ISNUMBER(value)	Checks if value is a number	=ISNUMBER(A1)
Returns TRUE	If value is a number	A1=100 → TRUE
Returns FALSE	If value is text, blank, or error	A2="text" → FALSE
Works with formulas	Checks formula results	=ISNUMBER(5+3) → TRUE

Key Takeaways

ISNUMBER returns TRUE only if the cell contains a numeric value.

Text that looks like numbers returns FALSE unless converted.

Use ISNUMBER to validate data before calculations.

Empty cells or errors return FALSE with ISNUMBER.

Combine ISNUMBER with other functions for powerful checks.