diff --git a/onnxruntime/test/perftest/posix/utils.cc b/onnxruntime/test/perftest/posix/utils.cc
index 9bf029d8dff35..09d62c6f5d808 100644
--- a/onnxruntime/test/perftest/posix/utils.cc
+++ b/onnxruntime/test/perftest/posix/utils.cc
@@ -17,7 +17,14 @@ namespace utils {
 std::size_t GetPeakWorkingSetSize() {
   struct rusage rusage;
   getrusage(RUSAGE_SELF, &rusage);
-  return static_cast<size_t>(rusage.ru_maxrss * 1024L);
+
+#if defined(__APPLE__)
+  constexpr size_t kBytesPerMaxRssUnit = 1;
+#else
+  constexpr size_t kBytesPerMaxRssUnit = 1024;
+#endif
+
+  return static_cast<size_t>(rusage.ru_maxrss) * kBytesPerMaxRssUnit;
 }
 
 class CPUUsage : public ICPUUsage {