diff --git a/lib/filesystem.js b/lib/filesystem.js
index 722ff40..a23547d 100755
--- a/lib/filesystem.js
+++ b/lib/filesystem.js
@@ -60,7 +60,7 @@ function fsSize(callback) {
           const size = parseInt(((_linux || _freebsd || _openbsd || _netbsd) ? line[2] : line[1])) * 1024;
           const used = parseInt(((_linux || _freebsd || _openbsd || _netbsd) ? line[3] : line[2])) * 1024;
           const available = parseInt(((_linux || _freebsd || _openbsd || _netbsd) ? line[4] : line[3])) * 1024;
-          const use = parseFloat((100.0 * ((_linux || _freebsd || _openbsd || _netbsd) ? line[3] : line[2]) / ((_linux || _freebsd || _openbsd || _netbsd) ? line[2] : line[1])).toFixed(2));
+          const use = parseFloat((100.0 * (used / (used + available)).toFixed(2)).toFixed(2));
           const mount = line[line.length - 1];
           if (!data.find(el => (el.fs === fs && el.type === fstype))) {
             data.push({