diff --git a/flang/runtime/numeric.cpp b/flang/runtime/numeric.cpp
--- a/flang/runtime/numeric.cpp
+++ b/flang/runtime/numeric.cpp
@@ -109,7 +109,7 @@
   } else if (x == 0) {
     return 0; // 0 -> 0
   } else {
-    int expo{std::ilogb(x)};
+    int expo{std::ilogb(x) + 1};
     auto ip{static_cast<int>(p - expo)};
     if (ip != p - expo) {
       ip = p < 0 ? std::numeric_limits<int>::min()
diff --git a/flang/unittests/Runtime/Numeric.cpp b/flang/unittests/Runtime/Numeric.cpp
--- a/flang/unittests/Runtime/Numeric.cpp
+++ b/flang/unittests/Runtime/Numeric.cpp
@@ -142,10 +142,10 @@
 TEST(Numeric, SetExponent) {
   EXPECT_EQ(RTNAME(SetExponent4)(Real<4>{0}, 0), 0);
   EXPECT_EQ(RTNAME(SetExponent8)(Real<8>{0}, 666), 0);
-  EXPECT_EQ(RTNAME(SetExponent8)(Real<8>{3.0}, 0), 1.5);
-  EXPECT_EQ(RTNAME(SetExponent4)(Real<4>{1.0}, 0), 1.0);
-  EXPECT_EQ(RTNAME(SetExponent4)(Real<4>{1.0}, 1), 2.0);
-  EXPECT_EQ(RTNAME(SetExponent4)(Real<4>{1.0}, -1), 0.5);
+  EXPECT_EQ(RTNAME(SetExponent8)(Real<8>{3.0}, 0), 0.75);
+  EXPECT_EQ(RTNAME(SetExponent4)(Real<4>{1.0}, 0), 0.5);
+  EXPECT_EQ(RTNAME(SetExponent4)(Real<4>{1.0}, 1), 1.0);
+  EXPECT_EQ(RTNAME(SetExponent4)(Real<4>{1.0}, -1), 0.25);
   EXPECT_TRUE(std::isnan(
       RTNAME(SetExponent4)(std::numeric_limits<Real<4>>::infinity(), 1)));
   EXPECT_TRUE(std::isnan(