---
type: "datatype"
title: "Ratio"
datatype: "Ratio"
---
# Ratio

- [Datatypes](/datatypes)
- [Definitions](/datatypes-definitions#Ratio)
- [Examples](/datatypes-examples#Ratio)
- [Mappings](/datatypes-mappings#Ratio)
- [Profiles](/datatypes-profiles#Ratio)

## Overview

See also [Examples](datatypes-examples#Ratio), [Detailed Descriptions](datatypes-definitions#Ratio), [Mappings](datatypes-mappings#Ratio), [Profiles](datatypes-profiles#Ratio) and [Extensions]([%extensions-location%]extensions-datatypes#Ratio)

A relationship between two Quantity values expressed as a numerator and a denominator.

The Ratio datatype should only be used to express a relationship of two numbers if the relationship cannot be suitably expressed using a Quantity and a common unit. Where the denominator value is known to be fixed to "1", Quantity should be used instead of Ratio.

\[%dt Ratio 6%\]

Examples where a Quantity is typically used are rates, densities, concentrations. Examples where a Ratio is used are: titers (e.g., 1:128); concentration ratios where the denominator is significant (e.g., 5mg/10mL); observed frequencies (e.g., 2 repetitions/8 hr), and where the numerator or denominator is an amount of a currency (no UCUM code for $ etc.).

Common factors in the numerator and denominator are not automatically cancelled out. Ratios are not simply "structured numbers" - for example, blood pressure measurements (e.g., "120/60") are not ratios.

A proper ratio has both a numerator and a denominator; however, these are not mandatory in order to allow an invalid ratio with an extension with further information.

**Constraints**

\[%dt.constraints Ratio%\]

The context of use may require particular types of Quantity for the numerator or denominator.

Ratio is used in the following places: \[%dtusage Ratio%\]

## Elements

- **[Ratio.numerator](/datatypes-definitions#Ratio.numerator)** [0..1]: [Quantity](/Quantity) The value of the numerator
- **[Ratio.denominator](/datatypes-definitions#Ratio.denominator)** [0..1]: [SimpleQuantity](/SimpleQuantity) The value of the denominator

## Mappings

- **Ratio.numerator**: RIM Mapping: .numerator
- **Ratio.denominator**: RIM Mapping: .denominator