# Defining metrics on-the-fly from others (custom metric types)

All metric values are defined by their metric type, area, and period.

Some metric types are derived from combinations of others. For example, the number of fires per household comes from the metric type giving the number of fires divided by the metric type giving the number of households. For the number of fires per 1,000 households, we just multiply the result by 1,000. For the number of fires per resident, we use the metric type defining the number of residents rather than the number of households.

Metric types giving these values are known as "custom metric types". They are represented by a formula rather than an integer. The formula has this syntax:

<*numerator*/*denominator***multiple*:*label*>

The numerator, the denominator, and the multiple represent metric type identifiers if followed by "M". They represent literal numbers if followed by "N". The label is a free text name for the custom metric types. The number of decimal places specified in the numerator gives the precision of the result.

You can add or subtract multiple items within the numerator or denominator.

### Example 1

Core spending power per dwelling is given by this custom metric type:

<5328M/22M*1000000.00N:Core spending Power per dwelling>

This has:

*numerator*metric type 5328 - Core Spending Power (Actual)*denominator*metric type 22 - Total number of dwellings in the area*multiple*number 1,000,000 with the result to two decimal places*label*the text "Core Spending Power per dwelling"

See values for this metric type in our Data Tool: https://developertools.esd.org.uk/data?value.valueType=raw&metricType=<5328M/22M*1000000.00N:Core spending Power per dwelling>&area=AllLaInCountry_England&period=fin_2021_22

### Example 2

Debt servicing as % of Core Spending Power is given by this custom metric type:

<7051M+7052M+7053M+7057M/5328M*0.1N:Debt servicing as % of Core Spending Power>

This has:

*numerator*metric types 7051 - Provision for repayment of principal (RS) PLUS 7052 - Leasing payments (RS) PLUS 7053 - Interest: Interest payable and similar charges (RS) PLUS 7057 - Private Finance Initiative (PFI) schemes - difference from service charge (RS)*denominator*metric type 5328 - Core Spending Power (Actual)*multiple*number 0.1 with the result to one decimal place*label*the text "Debt servicing as % of Core Spending Power"

See values for this metric type in our Data Tool: https://developertools.esd.org.uk/data?metricType=<7051M+7052M+7053M+7057M/5328M*0.1N:Debt servicing as % of Core Spending Power>&area=AllLaInCountry_England&period=latest

### Custom metric type dialog

When using the LG Inform Report Builder, you can construct a custom metric type using the "Custom metic type" dialog.