diff --git a/src/js/app/bitwise/calc.js b/src/js/app/bitwise/calc.js
index b87267b..385ccbc 100644
--- a/src/js/app/bitwise/calc.js
+++ b/src/js/app/bitwise/calc.js
@@ -5,6 +5,9 @@ app.set('calc', function() {
     return {
 
         numberOfBits: function (num) {
+            if(num < 0) {
+                return 32;
+            }
             should.bePositiveInteger(num);
             return Math.floor(Math.log(num) / Math.log(2)) + 1;
         },
diff --git a/src/js/app/bitwise/expression.js b/src/js/app/bitwise/expression.js
index 3e1fb0a..80028c9 100644
--- a/src/js/app/bitwise/expression.js
+++ b/src/js/app/bitwise/expression.js
@@ -1,8 +1,8 @@
 app.set('expression', function() {
     "use strict";
 
-    var exprRegex = /^(\d+|0x[\d,a-f]+)\s*(<<|>>|\||\&|\^)\s*(\d+|0x[\d,a-f]+)$/;
-    var listRegex = /^((\d+|0x[\d,a-f]+)\s?)+$/
+    var exprRegex = /^(-?(?:\d+|0x[\d,a-f]+))\s*(<<|>>|\||\&|\^)\s*(-?(?:\d+|0x[\d,a-f]+))$/;
+    var listRegex = /^(-?(?:\d+|0x[\d,a-f]+)\s?)+$/;
 
     return {
         canParse: function(string) {
@@ -73,10 +73,11 @@ app.set('expression', function() {
         this.input = input;
         this.value = parseInt(input);
         // console.log('value: ' + this.value);
-        this.hex = '0x' + this.value.toString(16);
+        var hex = this.value.toString(16);
+        this.hex = hex.indexOf('-') == 0 ? '-0x' + hex.substr(1) : '0x' + hex;
         this.dec = this.value.toString(10);
-        this.bin = this.value.toString(2);
-        this.kind = this.input.indexOf('0x') == 0 ? 'hex' : 'dec';
+        this.bin = (this.value>>>0).toString(2);
+        this.kind = this.input.indexOf('0x') > -1 ? 'hex' : 'dec';
         this.other = this.kind == 'dec' ? this.hex : this.dec;
     }
 
diff --git a/tests/domain/expressionSpec.js b/tests/domain/expressionSpec.js
index 045f697..f947c52 100644
--- a/tests/domain/expressionSpec.js
+++ b/tests/domain/expressionSpec.js
@@ -36,6 +36,7 @@ describe("expression parse", function() {
     });
 
     var listCases = {
+        '-0xa -9' : [-10, -9],
         '1 2 3': [1, 2, 3],
         '0x1 2 0xa6b': [0x1, 2, 0xa6b],
         '0x11a': [0x11a]
@@ -68,6 +69,17 @@ describe('create operands', function() {
     rundOperandsTest(hexOperand, decOperand);
 });
 
+describe('negative operands', function () {
+    var op = expression.parseOperand('-0xa');
+    it('shoold have correct values', function() {
+        expect(op.value).toBe(-10);
+        expect(op.hex).toBe('-0xa');
+        expect(op.bin).toBe('11111111111111111111111111110110');
+        expect(op.dec).toBe('-10');
+        expect(op.kind).toBe('hex');
+    })
+});
+
 function rundOperandsTest(hexOperand, decOperand) {
     it('should remember input form', function() {
         expect(hexOperand.input).toBe('0x10');