---
type: "fhirpath-function"
title: "FHIRPath Function: power"
function: "power"
category: "Math"
section: "5.8.7"
source: "fhirpath/functions.json"
---
# FHIRPath Function: power
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Raises a number to the `exponent` power.
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Accepts input types of Decimal, Integer or Long.
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The result is always a Decimal, because raising an Integer to a negative power (such as -1) produces a Decimal result.
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If the power cannot be represented (such as -1 raised to the 0.5), the result is empty.
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If the input is empty, or exponent is empty, the result is empty.
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If the input collection contains multiple items, the evaluation of the expression will end and signal an error to the calling environment.
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``` fhirpath
2.power(3) // 8
2.5.power(2) // 6.25
2.power(-1) // 0.5
(-1).power(0.5) // empty ({ })
```
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## Summary
- **Category**: Math
- **Section**: `5.8.7`
- **Return Type**: `Decimal`
- **Empty Input Result**: `empty`
- **Errors on Multiple Input**: `true`
## Description
Raises a number to the `exponent` power. This function can operate on Decimal and Integer types, but not on Quantity. If this function is used with Integers, the result is an Integer. If the function is used with Decimals, the result is a Decimal. If the function is used with a mixture of Integer and Decimal, the Integer is implicitly converted to a Decimal and the result is a Decimal. Note that if both the base and the `exponent` are integers and the `exponent` is negative, the result is empty since that might result in a Decimal value, not an Integer (the expected output type for this case). If the power cannot be represented (such as the -1 raised to the 0.5), the result is empty.
## Arguments
- `exponent`: `Integer | Decimal` - The exponent to raise the input number to
## Type Mapping
- `Integer-Decimal`
- `Long-Decimal`
- `Decimal-Decimal`
## Example
```fhirpath
2.power(3) // 8
2.5.power(2) // 6.25
(-1).power(0.5) // empty ({ })
```