diff --git a/CHANGELOG.md b/CHANGELOG.md
index d379b26..959755a 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,4 +1,9 @@
-#Changelog
+# Changelog
+
+## 3.0.0
+
+- Remove `String.parseTime`
+- Export function instead of object
 
 ## 2.0.0
 
@@ -6,7 +11,7 @@
 - Remove bower / browser specific integrations - This module can still be used client side using modern development tools like webpack, browserify etc.
 - use `node-style-guide` coding style
 
-##1.1.1
+## 1.1.1
 
 - src now uses ES6
 - use gulp instead of grunt
@@ -19,7 +24,7 @@
 - misc meta data updates
 - add sourcemaps
 
-##1.1.0
+## 1.1.0
 
 - add MIT license
 - add Changelog
diff --git a/README.md b/README.md
index 2152e97..790ebd2 100644
--- a/README.md
+++ b/README.md
@@ -20,21 +20,21 @@ npm install --save timestring
 ### Overview
 
 ```js
+var timestring = require('timestring');
+
 var str = '1h 15m';
-var time = str.parseTime();
+var time = timestring(str);
 
 console.log(time); // will log 4500
 ```
 
-In the example above `str` is just a plain old `String` object. A new method is added to the `String` objects prototype named `parseTime`. This method parses the string and returns a time based value.
-
-**By default the returned time value will be in seconds.**
+**By default the returned time value from `timestring` will be in seconds.**
 
 The time string can contain as many time groups as needed:
 
 ```js
 var str = '1d 3h 25m 18s';
-var time = str.parseTime();
+var time = timestring(str);
 
 console.log(time); // will log 98718
 ```
@@ -43,20 +43,11 @@ and can be as messy as you like:
 
 ```js
 var str = '1 d    3HOurS 25              min         1   8s';
-var time = str.parseTime();
+var time = timestring(str);
 
 console.log(time); // will log 98718
 ```
 
-As well as using the `String` objects `parseTime` method you can create a `Timestring` object and parse the string manually:
-
-```js
-var str = '1h 15m';
-var time = (new Timestring()).parse(str);
-
-console.log(time); // will log 4500
-```
-
 ### Keywords
 
 Timestring will parse the following keywords into time values:
@@ -73,14 +64,14 @@ Keywords can be used interchangeably:
 
 ```js
 var str = '1day 15h 20minutes 15s';
-var time = str.parseTime();
+var time = timestring(str);
 
 console.log(time); // will log 141615
 ```
 
 ### Return Time Value
 
-By default the return time value will be in seconds. This can be changed by passing one of the following strings as an argument to `String.parseTime` or `Timestring.parse`:
+By default the return time value will be in seconds. This can be changed by passing one of the following strings as an argument to `timestring`:
 
 1. `s` - Seconds
 2. `m` - Minutes
@@ -93,15 +84,9 @@ By default the return time value will be in seconds. This can be changed by pass
 ```js
 var str = '22h 16m';
 
-var hours = str.parseTime('h'); // 22.266666666666666
-var days = str.parseTime('d'); // 0.9277777777777778
-var weeks = str.parseTime('w'); // 0.13253968253968254
-
-// or
-
-var hours = (new Timestring()).parse(str, 'h'); // 22.266666666666666
-var days = (new Timestring()).parse(str, 'd'); // 0.9277777777777778
-var weeks = (new Timestring()).parse(str, 'w'); // 0.13253968253968254
+var hours = timestring(str, 'h'); // 22.266666666666666
+var days = timestring(str, 'd'); // 0.9277777777777778
+var weeks = timestring(str, 'w'); // 0.13253968253968254
 ```
 
 ### Optional Configuration
@@ -113,7 +98,7 @@ A few assumptions are made by default:
 3. There are 4 weeks per month
 4. There are 12 months per year
 
-These options can be changed by passing a options object as an argument to `String.parseTime` or to the `Timestring` objects constructor.
+These options can be changed by passing an options object as an argument to `timestring`.
 
 The following options are configurable:
 
@@ -124,17 +109,11 @@ The following options are configurable:
 
 ```js
 var str = '1d';
-
 var opts = {
 	hoursPerDay: 1
 }
 
-var time = str.parseTime('h', opts);
-
-// or
-
-var time = (new Timestring(opts)).parse(str, 'h');
-
+var time = timestring(str, 'h', opts);
 
 console.log(time); // will log 1
 ```
@@ -151,19 +130,8 @@ var opts = {
 	daysPerWeek: 5
 }
 
-// get time values from form input
-var today = document.querySelector('time-input').value,  // '1d'
-	thisWeek = document.querySelector('time-input').value; // '1w'
-
-// parse times
-var hoursToday = today.parseTime('h', opts),
-	daysThisWeek = thisWeek.parseTime('d', opts);
-
-// or
-
-var hoursToday = (new Timestring(opts)).parse(today, 'h'),
-	daysThisWeek = (new Timestring(opts)).parse(thisWeek, 'd');
-
+var hoursToday = timestring('1d', 'h', opts);
+var daysThisWeek = timestring('1w', 'd', opts);
 
 console.log(hoursToday); // will log 7.5
 console.log(daysThisWeek); // will log 5
diff --git a/index.js b/index.js
index 4ffc318..c29aad0 100644
--- a/index.js
+++ b/index.js
@@ -1,111 +1,142 @@
+var _ = require('lodash');
+
 /**
  * Exports
  */
 
-module.exports = Timestring;
+module.exports = parseTimestring;
 
 /**
- * Create a new Timestring instance
+ * Default options to use when parsing a timestring
  *
- * @param {Object} opts
- * @constructor
+ * @type {Object}
  */
 
-function Timestring(opts) {
-  var defaultOpts = {
-    hoursPerDay: 24,
-    daysPerWeek: 7,
-    weeksPerMonth: 4,
-    monthsPerYear: 12,
-  };
+var defaultOpts = {
+  hoursPerDay: 24,
+  daysPerWeek: 7,
+  weeksPerMonth: 4,
+  monthsPerYear: 12,
+};
 
-  opts = opts || {};
-  this.opts = defaultOpts;
-  for (var s in opts) { this.opts[s] = opts[s]; }
+/**
+ * Map of accepted strings to unit
+ *
+ * @type {Object}
+ */
 
-  this.units = {
-    s: ['s', 'sec', 'secs', 'second', 'seconds'],
-    m: ['m', 'min', 'mins', 'minute', 'minutes'],
-    h: ['h', 'hr', 'hrs', 'hour', 'hours'],
-    d: ['d', 'day', 'days'],
-    w: ['w', 'week', 'weeks'],
-    mth: ['mth', 'mths','month', 'months'],
-    y: ['y', 'yr', 'yrs', 'year', 'years'],
-  };
+var unitMap = {
+  s: ['s', 'sec', 'secs', 'second', 'seconds'],
+  m: ['m', 'min', 'mins', 'minute', 'minutes'],
+  h: ['h', 'hr', 'hrs', 'hour', 'hours'],
+  d: ['d', 'day', 'days'],
+  w: ['w', 'week', 'weeks'],
+  mth: ['mth', 'mths','month', 'months'],
+  y: ['y', 'yr', 'yrs', 'year', 'years'],
+};
 
-  this.unitValues = {
+/**
+ * Parse a timestring
+ *
+ * @param {string} string
+ * @param {string} [returnUnit]
+ * @param {Object} [opts]
+ * @return {number}
+ */
+
+function parseTimestring(string, returnUnit, opts) {
+  opts = _.extend(_.clone(defaultOpts), opts || {});
+
+  var totalSeconds = 0;
+  var unitValues = getUnitValues(opts);
+  var groups = string
+    .toLowerCase()
+    .replace(/[^\.\w+-]+/g, '')
+    .match(/[-+]?[0-9]+[a-z]+/g);
+
+  if (groups !== null) {
+    _.each(groups, function(group) {
+      var value = group.match(/[0-9]+/g)[0];
+      var unit = group.match(/[a-z]+/g)[0];
+
+      totalSeconds += getSeconds(value, unit, unitValues);
+    });
+  }
+
+  if (returnUnit) {
+    return convert(totalSeconds, returnUnit, unitValues);
+  }
+
+  return totalSeconds;
+}
+
+/**
+ * Get unit values based on the passed options
+ *
+ * @param {Object} opts
+ * @returns {Object}
+ */
+
+function getUnitValues(opts) {
+  var unitValues = {
     s: 1,
     m: 60,
     h: 3600,
   };
 
-  this.unitValues.d = this.opts.hoursPerDay * this.unitValues.h;
-  this.unitValues.w = this.opts.daysPerWeek * this.unitValues.d;
-  this.unitValues.mth = this.opts.weeksPerMonth * this.unitValues.w;
-  this.unitValues.y = this.opts.monthsPerYear * this.unitValues.mth;
+  unitValues.d = opts.hoursPerDay * unitValues.h;
+  unitValues.w = opts.daysPerWeek * unitValues.d;
+  unitValues.mth = opts.weeksPerMonth * unitValues.w;
+  unitValues.y = opts.monthsPerYear * unitValues.mth;
+
+  return unitValues;
 }
 
 /**
- * Parse a timestring
+ * Get the key for a unit
  *
- * @param  {string} string
- * @param  {string} returnUnit
- * @return {string}
+ * @param {string} unit
+ * @returns {string}
  */
 
-Timestring.prototype.parse = function parse(string, returnUnit) {
-  function getUnitKey(unit) {
-    for (var k in this.units) {
-      for (var u in this.units[k]) {
-        if (unit === this.units[k][u]) {
-          return k;
-        }
+function getUnitKey(unit) {
+  for (var k in unitMap) {
+    for (var u in unitMap[k]) {
+      if (unit === unitMap[k][u]) {
+        return k;
       }
     }
-
-    throw new Error('The unit [' + unit + '] is not supported by timestring');
   }
 
-  function convert(value, unit) {
-    var baseValue = this.unitValues[getUnitKey.call(this, unit)];
-
-    return value / baseValue;
-  }
-
-  function getSeconds(value, unit) {
-    var baseValue = this.unitValues[getUnitKey.call(this, unit)];
-
-    return value * baseValue;
-  }
-
-  var totalSeconds = 0;
-  var groups = string
-                .toLowerCase()
-                .replace(/[^\.\w+-]+/g, '')
-                .match(/[-+]?[0-9]+[a-z]+/g);
-
-  if (groups !== null) {
-    for (var i = 0; i < groups.length; i++) {
-      var g = groups[i];
-      var value = g.match(/[0-9]+/g)[0];
-      var unit = g.match(/[a-z]+/g)[0];
-
-      totalSeconds += getSeconds.call(this, value, unit);
-    }
-  }
-
-  return (returnUnit) ?
-    convert.call(this, totalSeconds, returnUnit) :
-    totalSeconds;
-};
+  throw new Error('The unit [' + unit + '] is not supported by timestring');
+}
 
 /**
- * Parse a timestring
+ *  Get the number of seconds for a value, based on the unit
  *
- * @param  {string} unit
- * @param  {Object} opts
- * @return {string}
+ * @param {number} value
+ * @param {string} unit
+ * @param {Object} unitValues
+ * @returns {number}
  */
-String.prototype.parseTime = function parseTime(unit, opts) {
-  return (new Timestring(opts)).parse(this, unit);
-};
+
+function getSeconds(value, unit, unitValues) {
+  var baseValue = unitValues[getUnitKey(unit)];
+
+  return value * baseValue;
+}
+
+/**
+ * Convert a value from its existing unit to a new unit
+ *
+ * @param {number} value
+ * @param {string} unit
+ * @param {Object} unitValues
+ * @returns {number}
+ */
+
+function convert(value, unit, unitValues) {
+  var baseValue = unitValues[getUnitKey(unit)];
+
+  return value / baseValue;
+}
diff --git a/package.json b/package.json
index dd56d9e..411b3ed 100644
--- a/package.json
+++ b/package.json
@@ -9,11 +9,12 @@
     "url": "git://github.com/mike182uk/timestring.git"
   },
   "scripts": {
+    "dev": "watch 'clear; npm test -s;' ./ -d",
     "sa": "jshint index.js && jscs index.js",
     "test": "mocha test.js"
   },
   "main": "index.js",
-  "version": "2.0.0",
+  "version": "3.0.0",
   "devDependencies": {
     "chai": "^3.4.1",
     "codeclimate-test-reporter": "^0.2.0",
@@ -22,6 +23,10 @@
     "jscs": "^2.8.0",
     "jshint": "^2.9.1",
     "mocha": "^2.2.4",
-    "mocha-lcov-reporter": "1.0.0"
+    "mocha-lcov-reporter": "1.0.0",
+    "watch": "^0.17.1"
+  },
+  "dependencies": {
+    "lodash": "^4.0.0"
   }
 }
diff --git a/test.js b/test.js
index 2e3f2fd..160971d 100644
--- a/test.js
+++ b/test.js
@@ -5,20 +5,18 @@ var timestring = require('./index');
 
 describe('timestring', function() {
   it('can parse a timestring', function() {
-    var ts = new timestring();
-
-    expect(ts.parse('1s')).to.equal(1);
-    expect(ts.parse('1m')).to.equal(60);
-    expect(ts.parse('1h')).to.equal(3600);
-    expect(ts.parse('1d')).to.equal(86400);
-    expect(ts.parse('1w')).to.equal(604800);
-    expect(ts.parse('1mth')).to.equal(2419200);
-    expect(ts.parse('1y')).to.equal(29030400);
+    expect(timestring('1s')).to.equal(1);
+    expect(timestring('1m')).to.equal(60);
+    expect(timestring('1h')).to.equal(3600);
+    expect(timestring('1d')).to.equal(86400);
+    expect(timestring('1w')).to.equal(604800);
+    expect(timestring('1mth')).to.equal(2419200);
+    expect(timestring('1y')).to.equal(29030400);
   });
 
   it('can return a value in a specified unit', function() {
-    expect((new timestring()).parse('5m', 's')).to.equal(300);
-    expect((new timestring()).parse('5m', 'm')).to.equal(5);
+    expect(timestring('5m', 's')).to.equal(300);
+    expect(timestring('5m', 'm')).to.equal(5);
   });
 
   it('uses the passed options instead of the defaults', function() {
@@ -29,35 +27,17 @@ describe('timestring', function() {
       monthsPerYear: 4
     };
 
-    var ts = new timestring(opts);
-
-    expect(ts.parse('1d', 'h')).to.equal(1);
-    expect(ts.parse('1w', 'd')).to.equal(2);
-    expect(ts.parse('1mth', 'w')).to.equal(3);
-    expect(ts.parse('1y', 'mth')).to.equal(4);
+    expect(timestring('1d', 'h', opts)).to.equal(1);
+    expect(timestring('1w', 'd', opts)).to.equal(2);
+    expect(timestring('1mth', 'w', opts)).to.equal(3);
+    expect(timestring('1y', 'mth', opts)).to.equal(4);
   });
 
   it('throws an error when an invalid unit is used in the timestring', function() {
-    var ts = new timestring();
-
-    expect(ts.parse.bind(ts, '1g')).to.throw(Error);
+    expect(function() { timestring('1g'); }).to.throw(Error);
   });
 
   it('can parse a messy time string', function() {
-    expect((new timestring()).parse('5   D a YS    4 h   2 0     mI  nS')).to.equal(447600);
-  });
-
-  it('should expose a method on String.prototype that will parse the string as a timestring', function(){
-    var str = '1min';
-
-    // no arguments passed
-    expect(str.parseTime()).to.equal(60);
-
-    // units argument passed
-    expect(str.parseTime('m')).to.equal(1);
-
-    // units + options argument passed
-    str = '5h';
-    expect(str.parseTime('d', { hoursPerDay: 5 })).to.equal(1);
+    expect(timestring('5   D a YS    4 h   2 0     mI  nS')).to.equal(447600);
   });
 });