Reliably get the fixed format of a float in Ruby, rather than exponential. BUT: don't use an extraordinarily large number of decimal places, else you'll likely get more precision than you need.

fixed_format.rb

# as a method
def fixed_format(float)
  return float if float.to_s['e'].nil?

  matches = float.to_s.scan(/(\d+)e\-(\d+)$/).first
            # exponent + number of trailing digits
  digits  = matches.last.to_i + matches.first.length
  ("%0.#{digits}f" % float).gsub(/0+$/, '')
end

float_formatter.rb

# or better, clearer, albeit a little more code: as a class
class FloatFormatter
  PATTERN = /(\d+)e\-(\d+)$/

  def initialize(float)
    @float = float
  end

  def fixed
    return float.to_s unless exponent_present?

    ("%0.#{decimal_places}f" % float).gsub(/0+$/, '')
  end

  private

  attr_reader :float

  def exponent_decimal_places
    float.to_s[PATTERN, 1].length
  end

  def exponent_factor
    float.to_s[PATTERN, 2].to_i
  end

  def exponent_present?
    float.to_s['e']
  end

  def decimal_places
    exponent_factor + exponent_decimal_places
  end
end