---
type: "fhirpath-function"
title: "FHIRPath Function: length"
function: "length"
category: "String Manipulation"
section: "5.6.13"
source: "fhirpath/functions.json"
---
# FHIRPath Function: length
Returns the number of characters in the input string. If the input collection is empty (`{ }`), the result is empty.

If the input collection contains multiple items, the evaluation of the expression will end and signal an error to the calling environment.
## Summary
- **Category**: String Manipulation
- **Section**: `5.6.13`
- **Return Type**: `Integer`
- **Empty Input Result**: `empty`
- **Errors on Multiple Input**: `true`
## Description
Returns the length of the input string. Returns the number of characters in the string.
## Arguments
- none
## Type Mapping
- `String-Integer`
## Example
```fhirpath
'abcdefg'.length() // 7
''.length() // 0
```