diff --git a/readme.md b/readme.md
index 007aed8..c761b36 100644
--- a/readme.md
+++ b/readme.md
@@ -73,6 +73,7 @@ var result = stringMath("2+2");
   * `/` division sign
   * `+` plus sign
   * `-` subtraction sign
+  * `%` modulo sign
   * `(` and `)` parentheses
 
 ##### `callback` **[Function]** *(optional)* *(synchronous)*
@@ -92,7 +93,7 @@ If the math formula is of correct type and is valid, it returns the [Number] res
 # Tips
 * the arithmetic **order of operations** is respected:
   * *parentheses first*
-  * *then division and multiplication (from left to right)*
+  * *then division, multiplication and modulo (from left to right)*
   * *then addition and subtraction (from left to right)*
 * the multiplication sign can be omitted before parentheses; `4(2+1)`; *equals to `4*(2+1)`*
 * the following signs combinations are allowed:
diff --git a/string-math.js b/string-math.js
index 80c74a2..06743cf 100644
--- a/string-math.js
+++ b/string-math.js
@@ -1,6 +1,6 @@
 function stringMath(eq, callback) {
   if (typeof eq !== 'string') return handleCallback(new TypeError('The [String] argument is expected.'), null);
-  const mulDiv = /([+-]?\d*\.?\d+(?:e[+-]\d+)?)\s*([*/])\s*([+-]?\d*\.?\d+(?:e[+-]\d+)?)/;
+  const mulDivMod = /([+-]?\d*\.?\d+(?:e[+-]\d+)?)\s*([*/%])\s*([+-]?\d*\.?\d+(?:e[+-]\d+)?)/;
   const plusMin = /([+-]?\d*\.?\d+(?:e[+-]\d+)?)\s*([+-])\s*([+-]?\d*\.?\d+(?:e[+-]\d+)?)/;
   const parentheses = /(\d)?\s*\(([^()]*)\)\s*/;
   var current;
@@ -14,21 +14,21 @@ function stringMath(eq, callback) {
   function fParentheses(eq) {
     while (eq.search(parentheses) !== -1) {
       eq = eq.replace(parentheses, function (a, b, c) {
-        c = fMulDiv(c);
+        c = fMulDivMod(c);
         c = fPlusMin(c);
         return typeof b === 'string' ? b + '*' + c : c;
       });
     }
-    eq = fMulDiv(eq);
+    eq = fMulDivMod(eq);
     eq = fPlusMin(eq);
     return eq;
   }
 
-  function fMulDiv(eq) {
-    while (eq.search(mulDiv) !== -1) {
-      eq = eq.replace(mulDiv, function (a) {
-        const sides = mulDiv.exec(a);
-        const result = sides[2] === '*' ? sides[1] * sides[3] : sides[1] / sides[3];
+  function fMulDivMod(eq) {
+    while (eq.search(mulDivMod) !== -1) {
+      eq = eq.replace(mulDivMod, function (a) {
+        const sides = mulDivMod.exec(a);
+        const result = sides[2] === '*' ? sides[1] * sides[3] : sides[2] === '/' ? sides[1] / sides[3] : sides[1] % sides [3];
         return result >= 0 ? '+' + result : result;
       });
     }
diff --git a/tests/scenarios.js b/tests/scenarios.js
index 897cfa0..8077e56 100644
--- a/tests/scenarios.js
+++ b/tests/scenarios.js
@@ -148,5 +148,27 @@ module.exports = [
   {expression:".5e+123 * .25e-123",result:0.125},
   {expression:"(2e+2)",result:200},
   {expression:"123/1000/2000/3000",result:2.05e-8},
-  {expression:"(2.5e-2*(.25e+2*(.05e+5*5e-2)))",result:156.25}
-];
\ No newline at end of file
+  {expression:"(2.5e-2*(.25e+2*(.05e+5*5e-2)))",result:156.25},
+  {expression:"10 % 3",result:1},
+  {expression:"7 % 2",result:1},
+  {expression:"15 % 4",result:3},
+  {expression:"-10 % 3",result:-1},
+  {expression:"-7 % 2",result:-1},
+  {expression:"-15 % 4",result:-3},
+  {expression:"10 % -3",result:1},
+  {expression:"7 % -2",result:1},
+  {expression:"15 % -4",result:3},
+  {expression:"-10 % -3",result:-1},
+  {expression:"-7 % -2",result:-1},
+  {expression:"-15 % -4",result:-3},
+  {expression:"(10 + 4) % 6",result:2},
+  {expression:"15 % (3 + 2)",result:0},
+  {expression:"(8 - 3) % (2 + 2)",result:1},
+  {expression:"((7 % 3) + (4 % 2)) % 2",result:1},
+  {expression:"10 % 3 + 5 % 2",result:2},
+  {expression:"((8 % 3) + 4) % (2 % 2 + 1)",result:0},
+  {expression:"((3 % 2) * 5) % 4",result:1},
+  {expression:"(6 + 7 * 2) % (3 + 1 * 2)",result:0},
+  {expression:"(9 % 4) * (6 % 2) - (8 % 3)",result:-2},
+  {expression:"(((15 % 6) + 8) * 2) % 7",result:1}
+];