# Fractional Quantities

In this example we will see how a fractional quantity can be represented in CovJSON. For that we use the sea ice area fraction.

Fractions in CovJSON are stored as a decimal number which is typically between 0 and 1. Percentages are fractions comparing a number to 100, which means they simply have a unit of `1/100`, which is often symbolized with the percentage sign `%`. Depending on how data values are stored, those two cases have to be distinguished.

First, we look at the case where the sea ice area fraction is stored as a decimal between 0 and 1:

``````{
"type" : "Parameter",
"unit" : {
"label": {
"en": "Ratio"
},
"symbol": {
"value": "1",
"type": "http://www.opengis.net/def/uom/UCUM/"
}
},
"observedProperty" : {
"id" : "http://vocab.nerc.ac.uk/standard_name/sea_ice_area_fraction/",
"label" : {
"en": "Sea ice area fraction"
},
"description": {
"en": "Sea ice area fraction is the area of the sea surface occupied by sea ice. It is also called 'sea ice concentration'."
}
}
}
``````

When the fraction is stored as a percentage, the unit has to be changed:

``````{
"type" : "Parameter",
"unit" : {
"label": {
"en": "Percent"
},
"symbol": {
"value": "%",
"type": "http://www.opengis.net/def/uom/UCUM/"
}
},
"observedProperty" : {
"id" : "http://vocab.nerc.ac.uk/standard_name/sea_ice_area_fraction/",
"label" : {
"en": "Sea ice area fraction"
},
"description": {
"en": "Sea ice area fraction is the area of the sea surface occupied by sea ice. It is also called 'sea ice concentration'."
}
}
}
``````

An equivalent to `"%"` for `unit.symbol.value` is `"1/100"`, both represent the same unit. However, for the sake of easier processing and increased readability the percentage sign should be used in that case.