diff --git a/include/rcutils/time.h b/include/rcutils/time.h
index 46f682ef..fa000c75 100644
--- a/include/rcutils/time.h
+++ b/include/rcutils/time.h
@@ -27,18 +27,18 @@ extern "C"
 #include "rcutils/visibility_control.h"
 
 /// Convenience macro to convert seconds to nanoseconds.
-#define RCUTILS_S_TO_NS(seconds) (seconds * (1000LL * 1000LL * 1000LL))
+#define RCUTILS_S_TO_NS(seconds) ((seconds) * (1000LL * 1000LL * 1000LL))
 /// Convenience macro to convert milliseconds to nanoseconds.
-#define RCUTILS_MS_TO_NS(milliseconds) (milliseconds * (1000LL * 1000LL))
+#define RCUTILS_MS_TO_NS(milliseconds) ((milliseconds) * (1000LL * 1000LL))
 /// Convenience macro to convert microseconds to nanoseconds.
-#define RCUTILS_US_TO_NS(microseconds) (microseconds * 1000LL)
+#define RCUTILS_US_TO_NS(microseconds) ((microseconds) * 1000LL)
 
 /// Convenience macro to convert nanoseconds to seconds.
-#define RCUTILS_NS_TO_S(nanoseconds) (nanoseconds / (1000LL * 1000LL * 1000LL))
+#define RCUTILS_NS_TO_S(nanoseconds) ((nanoseconds) / (1000LL * 1000LL * 1000LL))
 /// Convenience macro to convert nanoseconds to milliseconds.
-#define RCUTILS_NS_TO_MS(nanoseconds) (nanoseconds / (1000LL * 1000LL))
+#define RCUTILS_NS_TO_MS(nanoseconds) ((nanoseconds) / (1000LL * 1000LL))
 /// Convenience macro to convert nanoseconds to microseconds.
-#define RCUTILS_NS_TO_US(nanoseconds) (nanoseconds / 1000LL)
+#define RCUTILS_NS_TO_US(nanoseconds) ((nanoseconds) / 1000LL)
 /// Convenience macro for rcutils_steady_time_now(rcutils_time_point_value_t *).
 #define RCUTILS_STEADY_TIME rcutils_steady_time_now
 
diff --git a/test/test_time.cpp b/test/test_time.cpp
index ec855b68..03796be5 100644
--- a/test/test_time.cpp
+++ b/test/test_time.cpp
@@ -50,6 +50,75 @@ class TestTimeFixture : public ::testing::Test
   }
 };
 
+// Tests the rcutils time unit conversion macros.
+TEST_F(TestTimeFixture, test_rcutils_time_conversion_macros) {
+  // Note: 9007199254740993 or higher cannot be represented anymore by intermediate type double
+  // without a loss of precision.
+
+  // seconds to nanoseconds
+  EXPECT_EQ(RCUTILS_S_TO_NS(1), 1000000000ll);  // int
+  EXPECT_EQ(RCUTILS_S_TO_NS(0.2), 200000000.);  // double
+  EXPECT_EQ(RCUTILS_S_TO_NS(1 + 1), 2000000000ll);  // sum of ints
+  EXPECT_EQ(
+    RCUTILS_S_TO_NS(9007199.254740992),
+    9007199254740992.);  // maximum precision double (53 bits)
+  EXPECT_EQ(
+    RCUTILS_S_TO_NS(9007199.254740993),
+    9007199254740992.);  // value is truncated!
+
+  // milliseconds to nanoseconds
+  EXPECT_EQ(RCUTILS_MS_TO_NS(1), 1000000ll);  // int
+  EXPECT_EQ(RCUTILS_MS_TO_NS(0.2), 200000.);  // double
+  EXPECT_EQ(RCUTILS_MS_TO_NS(1 + 1), 2000000ll);  // sum of ints
+  EXPECT_EQ(
+    RCUTILS_MS_TO_NS(9007199254.740992),
+    9007199254740992.);  // maximum precision double (53 bits)
+  EXPECT_EQ(
+    RCUTILS_MS_TO_NS(9007199254.740993),
+    9007199254740994.);  // value is truncated!
+
+  // microseconds to nanoseconds
+  EXPECT_EQ(RCUTILS_US_TO_NS(1), 1000ll);  // int
+  EXPECT_EQ(RCUTILS_US_TO_NS(0.2), 200.);  // double
+  EXPECT_EQ(RCUTILS_US_TO_NS(1 + 1), 2000ll);  // sum of ints
+  EXPECT_EQ(
+    RCUTILS_US_TO_NS(9007199254740.992),
+    9007199254740992.);  // maximum precision double (53 bits)
+  EXPECT_EQ(
+    RCUTILS_US_TO_NS(9007199254740.993),
+    9007199254740992.);  // value is truncated!
+
+  // nanoseconds to seconds
+  EXPECT_EQ(RCUTILS_NS_TO_S(1000000000ll), 1ll);  // int64_t
+  EXPECT_EQ(RCUTILS_NS_TO_S(1000000042ll), 1ll);  // int64_t (truncated)
+  EXPECT_EQ(RCUTILS_NS_TO_S(-1999999999ll), -1ll);  // int64_t (truncated)
+  EXPECT_EQ(RCUTILS_NS_TO_S(200000000.), 0.2);  // double
+  EXPECT_EQ(RCUTILS_NS_TO_S(1.0 + 1.0), 0.000000002);  // sum of doubles
+  EXPECT_EQ(
+    RCUTILS_NS_TO_S(9007199254740992.),
+    9007199.254740992);  // maximum precision double (53 bits)
+
+  // nanoseconds to milliseconds
+  EXPECT_EQ(RCUTILS_NS_TO_MS(1000000ll), 1ll);  // int64_t
+  EXPECT_EQ(RCUTILS_NS_TO_MS(1000042ll), 1ll);  // int64_t (truncated)
+  EXPECT_EQ(RCUTILS_NS_TO_MS(-1999999ll), -1ll);  // int64_t (truncated)
+  EXPECT_EQ(RCUTILS_NS_TO_MS(200000.), 0.2);  // double
+  EXPECT_EQ(RCUTILS_NS_TO_MS(1.0 + 1.0), 0.000002);  // sum of doubles
+  EXPECT_EQ(
+    RCUTILS_NS_TO_MS(9007199254740992.),
+    9007199254.740992);  // maximum precision double (53 bits)
+
+  // nanoseconds to microseconds
+  EXPECT_EQ(RCUTILS_NS_TO_US(1000ll), 1ll);  // int64_t
+  EXPECT_EQ(RCUTILS_NS_TO_US(1042ll), 1ll);  // int64_t (truncated)
+  EXPECT_EQ(RCUTILS_NS_TO_US(-1999ll), -1ll);  // int64_t (truncated)
+  EXPECT_EQ(RCUTILS_NS_TO_US(200.), 0.2);  // double
+  EXPECT_EQ(RCUTILS_NS_TO_US(1.0 + 1.0), 0.002);  // sum of doubles
+  EXPECT_EQ(
+    RCUTILS_NS_TO_US(9007199254740992.),
+    9007199254740.992);  // maximum precision double (53 bits)
+}
+
 // Tests the rcutils_system_time_now() function.
 TEST_F(TestTimeFixture, test_rcutils_system_time_now) {
   rcutils_ret_t ret;