diff --git a/bare-arm/mpconfigport.h b/bare-arm/mpconfigport.h
index 912fae66fc..97e866bdb7 100644
--- a/bare-arm/mpconfigport.h
+++ b/bare-arm/mpconfigport.h
@@ -46,8 +46,6 @@
 
 // type definitions for the specific machine
 
-#define BYTES_PER_WORD (4)
-
 #define MICROPY_MAKE_POINTER_CALLABLE(p) ((void*)((mp_uint_t)(p) | 1))
 
 #define UINT_FMT "%lu"
diff --git a/cc3200/mpconfigport.h b/cc3200/mpconfigport.h
index a8dc0cfeb8..4d19900aee 100644
--- a/cc3200/mpconfigport.h
+++ b/cc3200/mpconfigport.h
@@ -200,7 +200,6 @@ extern const struct _mp_obj_module_t mp_module_ussl;
 
 
 // type definitions for the specific machine
-#define BYTES_PER_WORD                              (4)
 #define MICROPY_MAKE_POINTER_CALLABLE(p)            ((void*)((mp_uint_t)(p) | 1))
 #define MP_SSIZE_MAX                                (0x7FFFFFFF)
 
diff --git a/esp8266/mpconfigport.h b/esp8266/mpconfigport.h
index 07bd48f679..d40eaba91b 100644
--- a/esp8266/mpconfigport.h
+++ b/esp8266/mpconfigport.h
@@ -118,8 +118,6 @@
 
 // type definitions for the specific machine
 
-#define BYTES_PER_WORD (4)
-
 #define MICROPY_MAKE_POINTER_CALLABLE(p) ((void*)((mp_uint_t)(p)))
 
 #define MP_SSIZE_MAX (0x7fffffff)
diff --git a/examples/embedding/mpconfigport_minimal.h b/examples/embedding/mpconfigport_minimal.h
index 48d2008583..d16827fa32 100644
--- a/examples/embedding/mpconfigport_minimal.h
+++ b/examples/embedding/mpconfigport_minimal.h
@@ -119,8 +119,6 @@ typedef int mp_int_t; // must be pointer size
 typedef unsigned int mp_uint_t; // must be pointer size
 #endif
 
-#define BYTES_PER_WORD sizeof(mp_int_t)
-
 // Cannot include <sys/types.h>, as it may lead to symbol name clashes
 #if _FILE_OFFSET_BITS == 64 && !defined(__LP64__)
 typedef long long mp_off_t;
diff --git a/minimal/mpconfigport.h b/minimal/mpconfigport.h
index e08943860b..47fc984290 100644
--- a/minimal/mpconfigport.h
+++ b/minimal/mpconfigport.h
@@ -57,8 +57,6 @@
 
 // type definitions for the specific machine
 
-#define BYTES_PER_WORD (4)
-
 #define MICROPY_MAKE_POINTER_CALLABLE(p) ((void*)((mp_uint_t)(p) | 1))
 
 // This port is intended to be 32-bit, but unfortunately, int32_t for
diff --git a/mpy-cross/mpconfigport.h b/mpy-cross/mpconfigport.h
index 0f76510986..383de14399 100644
--- a/mpy-cross/mpconfigport.h
+++ b/mpy-cross/mpconfigport.h
@@ -100,8 +100,6 @@ typedef int mp_int_t; // must be pointer size
 typedef unsigned int mp_uint_t; // must be pointer size
 #endif
 
-#define BYTES_PER_WORD sizeof(mp_int_t)
-
 // Cannot include <sys/types.h>, as it may lead to symbol name clashes
 #if _FILE_OFFSET_BITS == 64 && !defined(__LP64__)
 typedef long long mp_off_t;
diff --git a/pic16bit/mpconfigport.h b/pic16bit/mpconfigport.h
index a0371a8ae3..e4113956b3 100644
--- a/pic16bit/mpconfigport.h
+++ b/pic16bit/mpconfigport.h
@@ -68,7 +68,6 @@
 // type definitions for the specific machine
 
 #define MP_ENDIANNESS_LITTLE        (1)
-#define BYTES_PER_WORD              (2)
 #define MPZ_DIG_SIZE                (8)
 
 // The xc16 compiler doesn't seem to respect alignment (!!) so we
diff --git a/py/mpconfig.h b/py/mpconfig.h
index 54cf0f3d3d..9c89fc18aa 100644
--- a/py/mpconfig.h
+++ b/py/mpconfig.h
@@ -1105,6 +1105,11 @@ typedef double mp_float_t;
 #define STATIC static
 #endif
 
+// Number of bytes in a word
+#ifndef BYTES_PER_WORD
+#define BYTES_PER_WORD (sizeof(mp_uint_t))
+#endif
+
 #define BITS_PER_BYTE (8)
 #define BITS_PER_WORD (BITS_PER_BYTE * BYTES_PER_WORD)
 // mp_int_t value with most significant bit set
diff --git a/qemu-arm/mpconfigport.h b/qemu-arm/mpconfigport.h
index f642c64287..974d3520b3 100644
--- a/qemu-arm/mpconfigport.h
+++ b/qemu-arm/mpconfigport.h
@@ -39,8 +39,6 @@
 
 // type definitions for the specific machine
 
-#define BYTES_PER_WORD (4)
-
 #define MICROPY_MAKE_POINTER_CALLABLE(p) ((void*)((mp_uint_t)(p) | 1))
 
 #define MP_SSIZE_MAX (0x7fffffff)
diff --git a/stmhal/mpconfigport.h b/stmhal/mpconfigport.h
index 339360baef..3f36831997 100644
--- a/stmhal/mpconfigport.h
+++ b/stmhal/mpconfigport.h
@@ -264,8 +264,6 @@ extern const struct _mp_obj_module_t mp_module_network;
 
 // type definitions for the specific machine
 
-#define BYTES_PER_WORD (4)
-
 #define MICROPY_MAKE_POINTER_CALLABLE(p) ((void*)((mp_uint_t)(p) | 1))
 
 #define MP_SSIZE_MAX (0x7fffffff)
diff --git a/teensy/mpconfigport.h b/teensy/mpconfigport.h
index 07f60c43f6..8c40220465 100644
--- a/teensy/mpconfigport.h
+++ b/teensy/mpconfigport.h
@@ -54,8 +54,6 @@ extern const struct _mp_obj_module_t time_module;
 
 // type definitions for the specific machine
 
-#define BYTES_PER_WORD (4)
-
 #define UINT_FMT "%u"
 #define INT_FMT "%d"
 
diff --git a/unix/mpconfigport.h b/unix/mpconfigport.h
index a858845945..7ecfc28c09 100644
--- a/unix/mpconfigport.h
+++ b/unix/mpconfigport.h
@@ -233,8 +233,6 @@ typedef unsigned int mp_uint_t; // must be pointer size
 #endif
 #endif
 
-#define BYTES_PER_WORD sizeof(mp_int_t)
-
 // Cannot include <sys/types.h>, as it may lead to symbol name clashes
 #if _FILE_OFFSET_BITS == 64 && !defined(__LP64__)
 typedef long long mp_off_t;
diff --git a/unix/mpconfigport_minimal.h b/unix/mpconfigport_minimal.h
index 65e35c8d99..788c8519d2 100644
--- a/unix/mpconfigport_minimal.h
+++ b/unix/mpconfigport_minimal.h
@@ -127,8 +127,6 @@ typedef int mp_int_t; // must be pointer size
 typedef unsigned int mp_uint_t; // must be pointer size
 #endif
 
-#define BYTES_PER_WORD sizeof(mp_int_t)
-
 // Cannot include <sys/types.h>, as it may lead to symbol name clashes
 #if _FILE_OFFSET_BITS == 64 && !defined(__LP64__)
 typedef long long mp_off_t;
diff --git a/windows/mpconfigport.h b/windows/mpconfigport.h
index 6156ad39ef..844e2618f4 100644
--- a/windows/mpconfigport.h
+++ b/windows/mpconfigport.h
@@ -128,8 +128,6 @@ typedef int mp_int_t; // must be pointer size
 typedef unsigned int mp_uint_t; // must be pointer size
 #endif
 
-#define BYTES_PER_WORD sizeof(mp_int_t)
-
 // Just assume Windows is little-endian - mingw32 gcc doesn't
 // define standard endianness macros.
 #define MP_ENDIANNESS_LITTLE (1)
diff --git a/zephyr/mpconfigport.h b/zephyr/mpconfigport.h
index e0586dcfc1..0949d1374d 100644
--- a/zephyr/mpconfigport.h
+++ b/zephyr/mpconfigport.h
@@ -99,8 +99,6 @@ typedef void *machine_ptr_t; // must be of pointer size
 typedef const void *machine_const_ptr_t; // must be of pointer size
 typedef long mp_off_t;
 
-#define BYTES_PER_WORD (sizeof(mp_int_t))
-
 #define MP_STATE_PORT MP_STATE_VM
 
 #define MICROPY_PORT_ROOT_POINTERS \
diff --git a/zephyr/mpconfigport_minimal.h b/zephyr/mpconfigport_minimal.h
index 04383f6e32..772335c0a1 100644
--- a/zephyr/mpconfigport_minimal.h
+++ b/zephyr/mpconfigport_minimal.h
@@ -85,8 +85,6 @@ typedef void *machine_ptr_t; // must be of pointer size
 typedef const void *machine_const_ptr_t; // must be of pointer size
 typedef long mp_off_t;
 
-#define BYTES_PER_WORD (sizeof(mp_int_t))
-
 #define MP_STATE_PORT MP_STATE_VM
 
 #define MICROPY_PORT_ROOT_POINTERS \