diff --git a/README.md b/README.md
index 27b668c..0be5bd3 100644
--- a/README.md
+++ b/README.md
@@ -175,6 +175,8 @@ I also created a nice little command line tool called [mmon][mmon-github-url] (m
 | | governor | X | | | |  | e.g. 'powersave' |
 | | cores | X | X | X | X |  | # cores |
 | | physicalCores | X | X | X | X |  | # physical cores |
+| | efficiencyCores |   |   | X |  |  | # efficiancy cores (ARM only) |
+| | performanceCores |   |   | X |  |  | # performance cores (ARM only) |
 | | processors | X | X | X | X |  | # processors |
 | | socket | X | X |  | X |  | socket type e.g. "LGA1356" |
 | | vendor | X | X | X | X |  | vendor ID |
diff --git a/docs/cpu.html b/docs/cpu.html
index 64b29e6..22272fd 100644
--- a/docs/cpu.html
+++ b/docs/cpu.html
@@ -155,6 +155,26 @@
                     <td></td>
                     <td># physical cores</td>
                   </tr>
+                  <tr>
+                    <td></td>
+                    <td>efficiencyCores</td>
+                    <td></td>
+                    <td></td>
+                    <td>X</td>
+                    <td></td>
+                    <td></td>
+                    <td># efficiency cores (ARM only)</td>
+                  </tr>
+                  <tr>
+                    <td></td>
+                    <td>performanceCores</td>
+                    <td></td>
+                    <td></td>
+                    <td>X</td>
+                    <td></td>
+                    <td></td>
+                    <td># performance cores (ARM only)</td>
+                  </tr>
                   <tr>
                     <td></td>
                     <td>processors</td>
diff --git a/lib/cpu.js b/lib/cpu.js
index e334894..4939076 100644
--- a/lib/cpu.js
+++ b/lib/cpu.js
@@ -15,6 +15,7 @@
 
 const os = require('os');
 const exec = require('child_process').exec;
+const execSync = require('child_process').execSync;
 const fs = require('fs');
 const util = require('./util');
 
@@ -432,7 +433,12 @@ function getCpu() {
           const countCores = util.getValue(lines, 'hw.physicalcpu_max');
           const countThreads = util.getValue(lines, 'hw.ncpu');
           if (os.arch === 'arm64') {
+            const clusters = execSync('ioreg -c IOPlatformDevice -d 3 -r | grep cluster-type').toString().split('\n');
+            const efficiencyCores = clusters.filter(line => line.indexOf('"E"') >= 0).length;
+            const performanceCores = clusters.filter(line => line.indexOf('"P"') >= 0).length;
             result.socket = 'SOC';
+            result.efficiencyCores = efficiencyCores;
+            result.performanceCores = performanceCores;
           }
           if (countProcessors) {
             result.processors = parseInt(countProcessors) || 1;
diff --git a/lib/index.d.ts b/lib/index.d.ts
index 8179aec..f426e08 100644
--- a/lib/index.d.ts
+++ b/lib/index.d.ts
@@ -73,6 +73,8 @@ export namespace Systeminformation {
     governor: string;
     cores: number;
     physicalCores: number;
+    efficiencyCores?: number;
+    performanceCores?: number;
     processors: number;
     socket: string;
     cache: CpuCacheData;