Formatting a number as currency is easy thanks to the number_to_currency helper. This helper will take a valid number and format it as currency. It acceps a number of different options that allow complete customization of the displayed value.

number_to_currency(number, options = {})
Options
  • :locale - The locale option allows you to specify the locale you wish to use. Defaults to the current locale.
  • :precision - Sets the level of precision. Defaults to 2. Precision is the number of decimal places after the decimal.
  • :unit - Sets the denomination of the currency. For example: $ for the United States.
  • :separator - Specifies the separator to use between the units. For example the "." separates dollars and cents in the US.
  • :delimiter - Specifies the separator to use for the thousands delimiter. For example: 123,456.
  • :format - Sets the format for non-negative numbers. The current default is "%u%n". The %u specifies the currency ("$") and the %n specifies the number ("123,456")
  • :negative_format - Same as format, but applies to negative numbers.
  • :raise - If raise is set to true, an exception will be raised if the number isn't a valid number.
Examples
number_to_currency 123456.50                        # => $123,456.50
number_to_currency 123456.506                       # => $123,456.51
number_to_currency 123456.506, precision: 3         # => $123,456.506
number_to_currency "123a456"                        # => $123a456
number_to_currency "123a456", raise: true           # => ActionView::Helpers::NumberHelper::InvalidNumberError error
number_to_currency -123456.50, :negative_format => "(%u%n)"                               # => ($123,456.50)
number_to_currency 123456.50, unit: "£", seperator: ",", delimiter: ""                    # => £123456.50
number_to_currency 123456.50, unit: "£", separator: ",", delimiter: "", format: "%n %u"   # => 123456,50 £