diff --git a/calculator.rb b/calculator.rb
new file mode 100644
index 0000000..3253282
--- /dev/null
+++ b/calculator.rb
@@ -0,0 +1,77 @@
+def add(num1, num2)
+  return num1 + num2
+end
+
+def subtract(num1, num2)
+  return num1 - num2
+end
+
+def multiply(num1, num2)
+  return num1 * num2
+end
+
+def divide(num1, num2)
+  if num2 != 0
+    return num1 / num2
+  else
+    puts "Operation not possible. Division by zero is not allowed."
+  end
+end
+
+def modulo(num1, num2)
+  return num1 % num2
+end
+
+def exponify(num1, num2)
+  return num1 ** num2
+end
+
+puts "Enter the operation you would like:"
+operation = gets.chomp
+
+until ["add", "+", "subtract", "-", "multiply", "*", "divide", "/", "exponify", "**", "modulo", "%"].include?(operation)
+  puts "Please tell me to add (+), subtract (-), multiply (*), divide (/), exponify (**), or modulo (%)!"
+  operation = gets.chomp
+end
+
+puts "Enter the first number:"
+num1 = gets.chomp
+
+#regex to check for a numeral
+# lines 44-59 should be condensed into a method somehow
+while num1 !~ /^-?[0-9]+$/
+  puts "Please enter a valid number:"
+  num1 = gets.chomp
+end
+
+num1 = num1.to_f
+
+puts "Enter the second number:"
+num2 = gets.chomp
+
+while num2 !~ /^-?[0-9]+$/
+  puts "Please enter a valid number:"
+  num2 = gets.chomp
+end
+
+num2 = num2.to_f
+
+# case statements only accept strings (?)
+case operation
+  when "add", "+"
+  answer = add(num1,num2)
+  when "subtract", "-"
+  answer = subtract(num1,num2)
+  when "multiply", "*"
+  answer = multiply(num1,num2)
+  when "divide", "/"
+  answer = divide(num1,num2)
+  when "exponify", "**"
+  answer = exponify(num1,num2)
+  when "modulo", "%"
+  answer = modulo(num1,num2)
+  else
+  puts "Please enter a valid operation."
+end
+
+puts "Answer: #{answer}"