diff --git a/source/components/hardware/hwregs.c b/source/components/hardware/hwregs.c
index e90fd1482..b5b23831f 100644
--- a/source/components/hardware/hwregs.c
+++ b/source/components/hardware/hwregs.c
@@ -228,7 +228,7 @@ AcpiHwGetAccessBitWidth (
     }
     else if (Reg->AccessWidth)
     {
-        AccessBitWidth = (1 << (Reg->AccessWidth + 2));
+        AccessBitWidth = ACPI_ACCESS_BIT_WIDTH (Reg->AccessWidth);
     }
     else
     {
diff --git a/source/include/actypes.h b/source/include/actypes.h
index 843adec7f..da3288a9c 100644
--- a/source/include/actypes.h
+++ b/source/include/actypes.h
@@ -675,6 +675,13 @@ typedef UINT64                          ACPI_INTEGER;
 #define ACPI_VALIDATE_RSDP_SIG(a)       (!strncmp (ACPI_CAST_PTR (char, (a)), ACPI_SIG_RSDP, 8))
 #define ACPI_MAKE_RSDP_SIG(dest)        (memcpy (ACPI_CAST_PTR (char, (dest)), ACPI_SIG_RSDP, 8))
 
+/*
+ * Algorithm to obtain access bit width.
+ * Can be used with AccessWidth of ACPI_GENERIC_ADDRESS and AccessSize of
+ * ACPI_RESOURCE_GENERIC_REGISTER.
+ */
+#define ACPI_ACCESS_BIT_WIDTH(size)     (1 << ((size) + 2))
+
 
 /*******************************************************************************
  *