ATAN Function
Returns the angle (in radians) whose tangent is the supplied number.
Syntax
Parameters
| Parameter | Description | Required |
|---|---|---|
| number | The tangent of the angle you want; any real number is accepted. | Required |
Basic Example
Find the angle whose tangent is 1
=ATAN(1)The arctangent of 1 is π/4 radians (45°).
Advanced Examples
Example 1: Convert the result to degrees
Need the angle in degrees.Wrap ATAN in DEGREES.
=DEGREES(ATAN(1))Example 2: Use when you only know the slope
A line has slope 0.5; find its angle.Pass the slope directly.
=DEGREES(ATAN(0.5))How ATAN Works
ATAN is the inverse of TAN. For any real x it returns the unique angle θ in (-π/2, π/2) (radians) such that tan(θ) = x. It cannot distinguish opposite quadrants, so use ATAN2 when both coordinates are known.
Important Notes & Limitations
The result is in radians, not degrees.
ATAN uses only one argument, so it cannot tell which of two opposite quadrants the angle is in; ATAN2 resolves this with two coordinates.
Result range is limited to -π/2 to π/2.
Common Errors & Fixes
#VALUE!The argument is non-numeric text.Fix: Supply a numeric value or a numeric cell reference.
Download Practice File
ATAN
atanPractice ATAN with Real Data
Download a sample CSV file with pre-populated data and practice exercises for the ATAN function. Works in both Excel and Google Sheets.
File format: CSV (comma-separated values) - opens in Excel, Google Sheets, and all spreadsheet apps