diff --git a/src/js/tools.js b/src/js/tools.js
index 09d5e28..cd35b73 100644
--- a/src/js/tools.js
+++ b/src/js/tools.js
@@ -6,6 +6,12 @@ expandInp.oninput = expandChanged;
 let compressInp = document.getElementById('address_to_compress');
 compressInp.oninput = compressChanged;
 
+let macToEui64Inp = document.getElementById('mac_to_eui64_in');
+macToEui64Inp.oninput = macToEui64Changed;
+
+let eui64ToMacInp = document.getElementById('eui64_to_mac_in');
+eui64ToMacInp.oninput = eui64ToMacChanged;
+
 let ptrInp = document.getElementById('ptr_to_generate');
 ptrInp.oninput = ptrChanged;
 
@@ -52,6 +58,26 @@ function compressChanged(e){
 	}
 }
 
+function macToEui64Changed(e){
+   try {
+      $("#mac_to_eui64_out").text(encode_eui64($("#mac_to_eui64_in").val()));
+      $("#mac_to_eui64_in").parent().removeClass("has-warning");
+   }
+   catch {
+      $("#mac_to_eui64_in").parent().addClass("has-warning");
+   }
+}
+
+function eui64ToMacChanged(e){
+   try {
+      $("#eui64_to_mac_out").text(decode_eui64($("#eui64_to_mac_in").val()));
+      $("#eui64_to_mac_in").parent().removeClass("has-warning");
+   }
+   catch {
+      $("#eui64_to_mac_in").parent().addClass("has-warning");
+   }
+}
+
 function ptrChanged(e){
 	try {
 		$("#generated_ptr").html(ptr($("#ptr_to_generate").val()));
@@ -468,3 +494,32 @@ if (typeof module !== 'undefined' && typeof module.exports !== 'undefined') {
    window.ip6_randomSubnet = randomSubnet;
    window.ip6_ptr = ptr;
 }
+
+// Credits to iiidefix.net
+function decode_eui64(a) { // see rfc7042 Section 2.2
+  a = normalize(a).substring(20).replace(/:/g, '');
+  if (a.substring(6, 10) == 'fffe') {
+    a = a.split('');
+    a.splice(6, 4);
+    a[1] = (parseInt(a[1], 16) ^ 2).toString(16);
+    return a.join('').replace(/(..)/g, ':$1').substring(1);
+  }
+  else if (a.match(/^0[0123]005efe/)) {
+    return a.substring(8,16).replace(/(..)/g, x => parseInt(x, 16)+'.').replace(/\.$/, '');
+  }
+  else throw new Error('Invalid address: ' + a);
+}
+
+function encode_eui64(a) {
+  if (a.match(/^([0-9a-f]{2}[:.-]?){6}$/i)) {
+    a = a.replace(/[:.-]/g, '').split("");
+    a.splice(6, 0, 'fffe');
+    a[1] = (parseInt(a[1], 16) ^ 2).toString(16);
+    return abbreviate('fe80:' + a.join('').replace(/(....)/g, ':$1'));
+  }
+  else if (a.match(/^((25[0-5]|(2[0-4]|1\d|[1-9]|)\d)\.?\b){4}$/)) {
+    a = a.split('.').map(x => _leftPad(parseInt(x).toString(16), '0', 2));
+    return abbreviate('fe80::0200:5efe'+a.join('').replace(/(....)/g, ':$1'));
+  }
+  else throw new Error('Invalid address: ' + a);
+}
diff --git a/src/tools.html b/src/tools.html
index 03957a4..aee5e06 100644
--- a/src/tools.html
+++ b/src/tools.html
@@ -135,6 +135,50 @@
 						</div>
 					</div>
 				</div>
+				<div class="row">
+					<div class="col-md-6">
+						<div class="panel panel-default">
+							<div class="panel-heading">
+								<h3 class="panel-title">MAC to EUI-64</h3>
+							</div>
+							<div class="panel-body">
+								<table class="table">
+									<tr>
+										<td>
+											<input class="form-control address_in" id="mac_to_eui64_in" type="text" value="b5:9d:41:e9:8d:9d">
+										</td>
+									</tr>
+									<tr>
+										<td>
+											<div class="address_out" id="mac_to_eui64_out">fe80::b79d:41ff:fee9:8d9d</div>
+										</td>
+									</tr>
+								</table>
+							</div>
+						</div>
+					</div>
+					<div class="col-md-6">
+						<div class="panel panel-default">
+							<div class="panel-heading">
+								<h3 class="panel-title">EUI-64 to MAC</h3>
+							</div>
+							<div class="panel-body">
+								<table class="table">
+									<tr>
+										<td>
+											<input class="form-control address_in" id="eui64_to_mac_in" type="text" value="fe80::b79d:41ff:fee9:8d9d">
+										</td>
+									</tr>
+									<tr>
+										<td>
+											<div class="address_out" id="eui64_to_mac_out">b5:9d:41:e9:8d:9d</div>
+										</td>
+									</tr>
+								</table>
+							</div>
+						</div>
+					</div>
+				</div>
 				<div class="row">
 					<div class="col-md-12">
 						<div class="panel panel-default">
@@ -165,4 +209,4 @@
 		<script src="/js/vendor/bootstrap.min.js"></script>
 		<script src="/js/tools.js?v=3"></script>
 	</body>
-</html>
\ No newline at end of file
+</html>