diff --git a/examples/embedding/hello-embed.c b/examples/embedding/hello-embed.c
index 2000b703c1..9a90288cf6 100644
--- a/examples/embedding/hello-embed.c
+++ b/examples/embedding/hello-embed.c
@@ -53,7 +53,7 @@ mp_obj_t execute_from_str(const char *str) {
 
 int main() {
     // Initialized stack limit
-    mp_stack_set_limit(40000 * (BYTES_PER_WORD / 4));
+    mp_stack_set_limit(40000 * (sizeof(void *) / 4));
     // Initialize heap
     gc_init(heap, heap + sizeof(heap));
     // Initialize interpreter
diff --git a/mpy-cross/main.c b/mpy-cross/main.c
index a403c0504d..635e53a719 100644
--- a/mpy-cross/main.c
+++ b/mpy-cross/main.c
@@ -170,7 +170,7 @@ STATIC void pre_process_options(int argc, char **argv) {
                         heap_size *= 1024 * 1024;
                     }
                     if (word_adjust) {
-                        heap_size = heap_size * BYTES_PER_WORD / 4;
+                        heap_size = heap_size * MP_BYTES_PER_OBJ_WORD / 4;
                     }
                 } else {
                     exit(usage(argv));
@@ -182,7 +182,7 @@ STATIC void pre_process_options(int argc, char **argv) {
 }
 
 MP_NOINLINE int main_(int argc, char **argv) {
-    mp_stack_set_limit(40000 * (BYTES_PER_WORD / 4));
+    mp_stack_set_limit(40000 * (sizeof(void *) / 4));
 
     pre_process_options(argc, argv);
 
diff --git a/ports/esp32/mpconfigport.h b/ports/esp32/mpconfigport.h
index 5ad5fa18a3..81f8297c50 100644
--- a/ports/esp32/mpconfigport.h
+++ b/ports/esp32/mpconfigport.h
@@ -221,7 +221,6 @@ struct mp_bluetooth_nimble_root_pointers_t;
 
 // type definitions for the specific machine
 
-#define BYTES_PER_WORD (4)
 #define MICROPY_MAKE_POINTER_CALLABLE(p) ((void *)((mp_uint_t)(p)))
 void *esp_native_code_commit(void *, size_t, void *);
 #define MP_PLAT_COMMIT_EXEC(buf, len, reloc) esp_native_code_commit(buf, len, reloc)
diff --git a/ports/nrf/mpconfigport.h b/ports/nrf/mpconfigport.h
index 581e83ef2f..c246c53dd5 100644
--- a/ports/nrf/mpconfigport.h
+++ b/ports/nrf/mpconfigport.h
@@ -201,8 +201,6 @@
 
 // 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/ports/unix/main.c b/ports/unix/main.c
index af4328a4db..07db8d22c6 100644
--- a/ports/unix/main.c
+++ b/ports/unix/main.c
@@ -387,7 +387,7 @@ STATIC void pre_process_options(int argc, char **argv) {
                         goto invalid_arg;
                     }
                     if (word_adjust) {
-                        heap_size = heap_size * BYTES_PER_WORD / 4;
+                        heap_size = heap_size * MP_BYTES_PER_OBJ_WORD / 4;
                     }
                     // If requested size too small, we'll crash anyway
                     if (heap_size < 700) {
@@ -446,7 +446,7 @@ MP_NOINLINE int main_(int argc, char **argv) {
     signal(SIGPIPE, SIG_IGN);
     #endif
 
-    mp_stack_set_limit(40000 * (BYTES_PER_WORD / 4));
+    mp_stack_set_limit(40000 * (sizeof(void *) / 4));
 
     pre_process_options(argc, argv);
 
diff --git a/ports/unix/mpthreadport.c b/ports/unix/mpthreadport.c
index de0f5923ba..cbc4901f69 100644
--- a/ports/unix/mpthreadport.c
+++ b/ports/unix/mpthreadport.c
@@ -206,7 +206,7 @@ void mp_thread_start(void) {
 void mp_thread_create(void *(*entry)(void *), void *arg, size_t *stack_size) {
     // default stack size is 8k machine-words
     if (*stack_size == 0) {
-        *stack_size = 8192 * BYTES_PER_WORD;
+        *stack_size = 8192 * sizeof(void *);
     }
 
     // minimum stack size is set by pthreads
diff --git a/py/binary.c b/py/binary.c
index 1847894b71..5c098b223d 100644
--- a/py/binary.c
+++ b/py/binary.c
@@ -321,7 +321,7 @@ void mp_binary_set_val(char struct_type, char val_type, mp_obj_t val_in, byte *p
                     double f;
             } fp_dp;
             fp_dp.f = mp_obj_get_float_to_d(val_in);
-            if (BYTES_PER_WORD == 8) {
+            if (MP_BYTES_PER_OBJ_WORD == 8) {
                 val = fp_dp.i64;
             } else {
                 int be = struct_type == '>';
@@ -342,7 +342,7 @@ void mp_binary_set_val(char struct_type, char val_type, mp_obj_t val_in, byte *p
 
             val = mp_obj_get_int(val_in);
             // zero/sign extend if needed
-            if (BYTES_PER_WORD < 8 && size > sizeof(val)) {
+            if (MP_BYTES_PER_OBJ_WORD < 8 && size > sizeof(val)) {
                 int c = (mp_int_t)val < 0 ? 0xff : 0x00;
                 memset(p, c, size);
                 if (struct_type == '>') {
diff --git a/py/emitbc.c b/py/emitbc.c
index c74b7fbc4d..d7e8e05f0f 100644
--- a/py/emitbc.c
+++ b/py/emitbc.c
@@ -36,7 +36,7 @@
 
 #if MICROPY_ENABLE_COMPILER
 
-#define BYTES_FOR_INT ((BYTES_PER_WORD * 8 + 6) / 7)
+#define BYTES_FOR_INT ((MP_BYTES_PER_OBJ_WORD * 8 + 6) / 7)
 #define DUMMY_DATA_SIZE (BYTES_FOR_INT)
 
 struct _emit_t {
diff --git a/py/gc.c b/py/gc.c
index be35dc2ccc..53a0d9da4a 100644
--- a/py/gc.c
+++ b/py/gc.c
@@ -49,7 +49,7 @@
 // detect untraced object still in use
 #define CLEAR_ON_SWEEP (0)
 
-#define WORDS_PER_BLOCK ((MICROPY_BYTES_PER_GC_BLOCK) / BYTES_PER_WORD)
+#define WORDS_PER_BLOCK ((MICROPY_BYTES_PER_GC_BLOCK) / MP_BYTES_PER_OBJ_WORD)
 #define BYTES_PER_BLOCK (MICROPY_BYTES_PER_GC_BLOCK)
 
 // ATB = allocation table byte
diff --git a/py/mpconfig.h b/py/mpconfig.h
index 3a0c5fb6e7..e87c52f2be 100644
--- a/py/mpconfig.h
+++ b/py/mpconfig.h
@@ -126,7 +126,7 @@
 // Number of bytes in memory allocation/GC block. Any size allocated will be
 // rounded up to be multiples of this.
 #ifndef MICROPY_BYTES_PER_GC_BLOCK
-#define MICROPY_BYTES_PER_GC_BLOCK (4 * BYTES_PER_WORD)
+#define MICROPY_BYTES_PER_GC_BLOCK (4 * MP_BYTES_PER_OBJ_WORD)
 #endif
 
 // Number of words allocated (in BSS) to the GC stack (minimum is 1)
@@ -1530,9 +1530,9 @@ 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))
+// Number of bytes in an object word: mp_obj_t, mp_uint_t, mp_uint_t
+#ifndef MP_BYTES_PER_OBJ_WORD
+#define MP_BYTES_PER_OBJ_WORD (sizeof(mp_uint_t))
 #endif
 
 // Number of bits in a byte
@@ -1540,7 +1540,7 @@ typedef double mp_float_t;
 #define MP_BITS_PER_BYTE (8)
 #endif
 // mp_int_t value with most significant bit set
-#define WORD_MSBIT_HIGH (((mp_uint_t)1) << (BYTES_PER_WORD * 8 - 1))
+#define WORD_MSBIT_HIGH (((mp_uint_t)1) << (MP_BYTES_PER_OBJ_WORD * MP_BITS_PER_BYTE - 1))
 
 // Make sure both MP_ENDIANNESS_LITTLE and MP_ENDIANNESS_BIG are
 // defined and that they are the opposite of each other.
diff --git a/py/persistentcode.c b/py/persistentcode.c
index 084632a60f..ac523990c1 100644
--- a/py/persistentcode.c
+++ b/py/persistentcode.c
@@ -595,7 +595,7 @@ STATIC void mp_print_bytes(mp_print_t *print, const byte *data, size_t len) {
     print->print_strn(print->data, (const char *)data, len);
 }
 
-#define BYTES_FOR_INT ((BYTES_PER_WORD * 8 + 6) / 7)
+#define BYTES_FOR_INT ((MP_BYTES_PER_OBJ_WORD * 8 + 6) / 7)
 STATIC void mp_print_uint(mp_print_t *print, size_t n) {
     byte buf[BYTES_FOR_INT];
     byte *p = buf + sizeof(buf);