diff --git a/calculator.rb b/calculator.rb
new file mode 100644
index 0000000..b7894f3
--- /dev/null
+++ b/calculator.rb
@@ -0,0 +1,68 @@
+# CALCULATOR
+# Program accepts user input to perform calculator evaluations.
+
+operators = { 
+  :addition => ["+", "plus", "add", "addition"],
+  :subtraction => ["-", "minus", "subtract", "subtraction"],
+  :multiplication => ["*", "times","multiply", "multiplication"],
+  :division => ["/", "divide","split","division"],
+  :mod => ["%", "mod","modulo"],
+  :exponentialize => ["^", "to the power of","exponential","exponentialize"]
+}
+
+def calculate(equation, operators)
+  case equation["operator"]
+    when *(operators[:addition])
+      puts "Answer: #{equation["left number"].to_f.round(2) + equation["right number"].to_f.round(2)}"
+    when *(operators[:subtraction])
+      puts "Answer: #{equation["left number"].to_f.round(2) - equation["right number"].to_f.round(2)}"
+    when *(operators[:multiplication])
+      puts "Answer: #{equation["left number"].to_f.round(2) * equation["right number"].to_f.round(2)}"
+    when *(operators[:division])
+      puts "Answer: #{equation["left number"].to_f.round(2) / equation["right number"].to_f.round(2)}"
+    when *(operators[:mod])
+      puts "Answer: #{equation["left number"].to_f.round(2) % equation["right number"].to_f.round(2)}"
+    when *(operators[:exponentialize])
+      puts "Answer: #{equation["left number"].to_f.round(2) ** equation["right number"].to_f.round(2)}"
+    else
+      puts "Nothing to evaluate."
+  end
+end
+
+puts "CALCULATOR"
+puts "**********\n\n"
+puts "Welcome to the CALCULATOR. Available operators include:\n\n"
+
+operators.each do |k,v|
+  puts "#{k}: #{v.join(", ")}"
+end
+
+puts "********\n\n"
+
+equation = {
+  "operator" => nil,
+  "left number" => nil,
+  "right number" => nil,
+}
+
+equation.each do |segment, value| #populate each part of the equation with user input, validating as you go
+  print "Please give me the #{segment.to_s} > "
+  input = gets.strip
+
+  if segment == "operator" 
+    until operators.any? { |keys, values| values.include?(input)} 
+      print "Invalid operator. Try again. > "
+      input = gets.strip
+    end
+  else 
+    until input.to_f.to_s == input || input.to_i.to_s == input || '%.2f' % input.to_f.to_s == input 
+      puts "Whoops, '#{input}' (#{input.class}) is not a valid number. Please try again."
+      input = gets.strip
+    end
+  end
+  equation[segment] = input
+
+end
+
+puts "\n\nEvaluating the following input: #{equation["left number"]} #{equation["operator"]} #{equation["right number"]}"
+puts calculate(equation, operators)