Float

Float.new, Float()

Returns: Float · Updated March 13, 2026 · Core Classes

numbers floating-point numeric precision

The Float class represents floating-point numbers in Ruby, following the IEEE 754 double-precision format. Floats are used when you need decimal numbers with fractional parts.

Creating Floats

# Direct assignment
x = 3.14159
y = -2.5
z = 1.0

# Using Float() conversion
Float(42)      # => 42.0
Float("3.14")  # => 3.14

# From integers
100.to_f       # => 100.0

# Scientific notation
1e5            # => 100000.0
1.5e-3        # => 0.0015

Float Methods

# Infinite and NaN checks
(1.0 / 0).infinite?  # => 1 (positive infinity)
(-1.0 / 0).infinite? # => -1 (negative infinity)
(0.0 / 0).nan?       # => true (Not a Number)

# Rounding
3.14159.round(2)    # => 3.14
3.14159.floor       # => 3
3.14159.ceil        # => 4

# Conversion
3.14159.to_i        # => 3 (truncates)
3.14159.to_s        # => "3.14159"

Precision Considerations

# Floating-point precision issues
0.1 + 0.2  # => 0.30000000000000004

# Use BigDecimal for precision
require 'bigdecimal'
BigDecimal("0.1") + BigDecimal("0.2")
# => 0.3 (exact)

# Comparing floats
a = 0.1 + 0.2
b = 0.3
(a - b).abs < 0.0001  # => true (tolerance comparison)

Practical Examples

Mathematical Operations

# Basic math
2.5 + 1.5    # => 4.0
3.0 * 4.0    # => 12.0
10.0 / 3.0   # => 3.3333333333333335
5.0 ** 2     # => 25.0

# Using Math module
Math.sqrt(16.0)   # => 4.0
Math.sin(Math::PI / 2)  # => 1.0
Math.log(Math::E)       # => 1.0

Working with Currency (use BigDecimal in production)

# Simple price calculations (warning: precision issues!)
price = 19.99
tax = price * 0.08
total = price + tax
# => 21.5892

# Rounding for display
puts "Total: $#{total.round(2)}"  # => Total: $21.59

Temperature Conversion

def celsius_to_fahrenheit(c)
  c * 9.0 / 5 + 32
end

def fahrenheit_to_celsius(f)
  (f - 32) * 5.0 / 9
end

celsius_to_fahrenheit(100)    # => 212.0
fahrenheit_to_celsius(32)      # => 0.0

Division Behavior

# Integer vs float division
5 / 2       # => 2 (integer division)
5.0 / 2     # => 2.5
5 / 2.0     # => 2.5
5.0 / 2.0   # => 2.5

Special Values

# Infinity
Float::INFINITY     # => Infinity
1.0 / 0             # => Infinity
Float::INFINITY > Float::INFINITY  # => false

# Negative infinity
-1.0 / 0            # => -Infinity

# Not a Number (NaN)
0.0 / 0             # => NaN
Math.sqrt(-1)       # => NaN

Floats are essential for scientific computing, graphics, and any application requiring decimal math, but be aware of their precision limitations.