diff --git a/ext/elementwise.c b/ext/elementwise.c
index 7cb07bd..9cac2d0 100644
--- a/ext/elementwise.c
+++ b/ext/elementwise.c
@@ -259,6 +259,89 @@ VALUE nm_sin(VALUE self){
   return Data_Wrap_Struct(NMatrix, NULL, nm_free, result);
 }
 
+/*
+ *  Elementwise sum operator.
+ *  Takes in the given matrix
+ *  and returns the sum of all the elements of the matrix
+*/
+VALUE nm_sum(VALUE self){
+  nmatrix* input;
+  Data_Get_Struct(self, nmatrix, input);
+
+  VALUE result;
+
+
+  switch(input->dtype){
+    case nm_bool:
+    {
+      bool* input_elements = (bool*)input->elements;
+      int sum = 0;
+      for(size_t index = 0; index < input->count; index++)
+      {
+        sum += input_elements[index];
+      }
+      result = INT2NUM(sum);
+      break;
+    }
+    case nm_int:
+    {
+      int* input_elements = (int*)input->elements;
+      int sum = 0;
+      for(size_t index = 0; index < input->count; index++){
+        sum += input_elements[index];
+      }
+      result = INT2NUM(sum);
+      break;
+    }
+    case nm_float32:
+    {
+      float* input_elements = (float*)input->elements;
+      float sum = 0;
+      for(size_t index = 0; index < input->count; index++){
+        sum += sin(input_elements[index]);
+      }
+      result = DBL2NUM((double)sum);
+      break;
+    }
+    case nm_float64:
+    {
+      double* input_elements = (double*)input->elements;
+      double sum = 0;
+      for(size_t index = 0; index < input->count; index++){
+        sum += input_elements[index];
+      }
+      result = DBL2NUM(sum);
+      break;
+    }
+    case nm_complex32:
+    {
+      complex float* input_elements = (complex float*)input->elements;
+      complex float sum = 0 + 0*I;
+      for(size_t index = 0; index < input->count; index++){
+        sum += input_elements[index];
+      }
+      double real = (double)creal(sum);
+      double imag = (double)cimag(sum);
+      result = rb_Complex(DBL2NUM(real), DBL2NUM(imag));
+      break;
+    }
+    case nm_complex64:
+    {
+      complex double* input_elements = (complex double*)input->elements;
+      complex double sum = 0 + 0*I;
+      for(size_t index = 0; index < input->count; index++){
+        sum += input_elements[index];
+      }
+      double real = creal(sum);
+      double imag = cimag(sum);
+      result = rb_Complex(DBL2NUM(real), DBL2NUM(imag));
+      break;
+    }
+  }
+
+  return result;
+}
+
 #define DEF_UNARY_RUBY_ACCESSOR(oper, name)                        \
 static VALUE nm_##name(VALUE self) {                               \
   nmatrix* input;                                                  \
diff --git a/ext/ruby_nmatrix.c b/ext/ruby_nmatrix.c
index e5ac74b..0659c07 100644
--- a/ext/ruby_nmatrix.c
+++ b/ext/ruby_nmatrix.c
@@ -384,6 +384,7 @@ DECL_ELEMENTWISE_RUBY_ACCESSOR(divide)
 
 
 VALUE nm_sin(VALUE self);
+VALUE nm_sum(VALUE self);
 
 #define DECL_UNARY_RUBY_ACCESSOR(name)          static VALUE nm_##name(VALUE self);
 DECL_UNARY_RUBY_ACCESSOR(cos)
@@ -609,6 +610,7 @@ void Init_nmatrix() {
   rb_define_method(NMatrix, "*", nm_multiply, 1);
   rb_define_method(NMatrix, "/", nm_divide, 1);
 
+  rb_define_method(NMatrix, "sum", nm_sum, 0);
   rb_define_method(NMatrix, "sin", nm_sin, 0);
   rb_define_method(NMatrix, "cos", nm_cos, 0);
   rb_define_method(NMatrix, "tan", nm_tan, 0);
diff --git a/test/elementwise_test.rb b/test/elementwise_test.rb
index 7342b76..f98394f 100644
--- a/test/elementwise_test.rb
+++ b/test/elementwise_test.rb
@@ -11,6 +11,8 @@ def setup
 
     @boolean_left = NMatrix.new  [2,2],[true, false, true, false], :nm_bool
     @boolean_right = NMatrix.new [2,2],[true, true, false, false], :nm_bool
+
+    @int = NMatrix.new [2, 2], [1, 2, 3, 4], :nm_int
   end
 
   def test_add
@@ -49,6 +51,30 @@ def test_subtract
     assert_equal answer, result
   end
 
+  def test_sum
+    result = 12.4
+    answer = @left.sum
+    assert_in_delta answer, result, 0.01
+  end
+
+  def test_sum_bool
+    result = 2
+    answer = @boolean_left.sum
+    assert_equal answer, result
+  end
+
+  def test_sum_int
+    result = 10
+    answer = @int.sum
+    assert_equal answer, result
+  end
+
+  def test_sum_complex
+    result = (12.4 + 0.0i)
+    answer = @complex_left.sum
+    assert_in_delta answer, result, 0.01
+  end
+
   def test_sin
     result = NMatrix.new [2,2], @left.elements.map{ |x| Math.send(:sin, x) }
     answer = @left.sin
@@ -66,5 +92,4 @@ def test_tan
     answer = @left.tan
     assert_equal answer, result
   end
-
 end
diff --git a/test/nmatrix_test.rb b/test/nmatrix_test.rb
index 1281d3f..3271a80 100644
--- a/test/nmatrix_test.rb
+++ b/test/nmatrix_test.rb
@@ -59,5 +59,4 @@ def test_slicing
     assert_equal @m[0, 0..1, 0..1], @s
     assert_equal @m_int[0, 0..1, 0..1], @s_int
   end
-
 end