---
type: "fhirpath-function"
title: "FHIRPath Function: sqrt"
function: "sqrt"
category: "Math"
section: "5.8.9"
source: "fhirpath/functions.json"
---
# FHIRPath Function: sqrt
{:.stu}

Returns the square root of the input number.
{:.stu}

Accepts Decimal input types. Integer and Long types are also accepted via implicit conversion to Decimal. 
{:.stu}

If the square root cannot be represented (such as the square root of -1), the result is empty.
{:.stu}

If the input collection is empty, the result is empty.
{:.stu}

If the input collection contains multiple items, the evaluation of the expression will end and signal an error to the calling environment.
{:.stu}

Note that this function is equivalent to raising a number of the power of 0.5 using the power() function.
{:.stu}

``` fhirpath
81.sqrt() // 9.0
(-1).sqrt() // empty
```
{:.stu}
## Summary
- **Category**: Math
- **Section**: `5.8.9`
- **Return Type**: `Decimal`
- **Empty Input Result**: `empty`
- **Errors on Multiple Input**: `true`
## Description
Returns the square root of the input number as a Decimal.
## Arguments
- none
## Type Mapping
- `Integer-Decimal`
- `Long-Decimal`
- `Decimal-Decimal`
## Example
```fhirpath
81.sqrt() // 9.0
(-1).sqrt() // empty
```