Your Molecular Formula

List of allowed groups

Apply Gaussian:
Reference version:

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Resolution = M / ΔM


Monoisotopic mass

This service allows to retrieve possible molecular formula from an experimental monoisotopic mass. The communication between the browser and the server use AJAX protocol. Because of the protection it is required to add on your server a "Proxy" that allows to prevent any security exception.


You may implement our tools for free on your server at the condition that you provide a link to "".

On your server edit httpd.conf and add the following line:

ProxyPass /chemcalc
You may now download the example file and install it on your server. To download the file just right click on this link and save to your computer. The result of the page is show just bellow. Just enter a monoisotopic mass and click on "Search molecular formula".

Main script code

The system use jquery.js and the following example code:

<script language="javascript">
	function getMFFromMonoisotopicMass() {
		var monoisotopicMass=$('#experimental').val()*1;
		var mfRange=$('#mfRange').val();
		var parameters={monoisotopicMass: monoisotopicMass, mfRange: mfRange, action: "em2mf"};
		$.getJSON('/chemcalc', parameters, function(result) {
			var results=result.results;
			if (results) {
				var size=results.length;
				var toReturn=[];
				toReturn.push("<table width=520><tr><th>MF</th><th>Monoisotopic mass</th><th>PPM</th><th>mDa</th><th>Unsaturation</th></tr>");
				for (var i=0; i<size; i++) {
					var ppm=(results[i].error/results[i].em*1000000).toFixed(3);
					toReturn.push("<tr><td>"+results[i].mf.replace(/([0-9]+)/g,"<sub>$1</sub>")+"</td><td>"+results[i].em+"</td><td align='right'>"+ppm+"</td><td align='right'>"+(results[i].error*1000).toFixed(3)+"</td><td align='center'>"+results[i].unsat+"</td></tr>"); 



Mandatory parameters:

  • action: em2mf
  • monoisotopicMass:: the experimental monoisotopic mass

Optional filtering parameters:

  • mfRange: contains the range for allowed molecular formula. default: C0-20H0-40N0-5O0-8F0-3Cl0-3Br0-1
  • minUnsaturation: default: 0
  • maxUnsaturation: default: 40
  • integerUnsaturation:: true or false. default: false
  • minMass:: default: 100
  • maxMass:: default: 200
  • massRange:: default: 0.5


  • The maximal total number of iterations is currently 5000000.
  • The maximal number of returned rows is currently 1000.