diff --git a/esp8266/modpybspi.c b/esp8266/modpybspi.c
index acc3c25125..e974547111 100644
--- a/esp8266/modpybspi.c
+++ b/esp8266/modpybspi.c
@@ -36,10 +36,24 @@
 /******************************************************************************/
 // MicroPython bindings for SPI
 
+STATIC uint32_t baudrate_from_delay_half(uint32_t delay_half) {
+    return 500000 / delay_half;
+}
+
+STATIC uint32_t baudrate_to_delay_half(uint32_t baudrate) {
+    uint32_t delay_half = 500000 / baudrate;
+    // round delay_half up so that: actual_baudrate <= requested_baudrate
+    if (500000 % baudrate != 0) {
+        delay_half += 1;
+    }
+    return delay_half;
+}
+
 STATIC void pyb_spi_print(const mp_print_t *print, mp_obj_t self_in, mp_print_kind_t kind) {
     mp_machine_soft_spi_obj_t *self = MP_OBJ_TO_PTR(self_in);
     mp_printf(print, "SPI(baudrate=%u, polarity=%u, phase=%u, sck=%u, mosi=%u, miso=%u)",
-        self->baudrate, self->polarity, self->phase, self->sck, self->mosi, self->miso);
+        baudrate_from_delay_half(self->delay_half),
+        self->polarity, self->phase, self->sck, self->mosi, self->miso);
 }
 
 STATIC void pyb_spi_init_helper(mp_machine_soft_spi_obj_t *self, size_t n_args, const mp_obj_t *pos_args, mp_map_t *kw_args) {
@@ -56,7 +70,7 @@ STATIC void pyb_spi_init_helper(mp_machine_soft_spi_obj_t *self, size_t n_args,
     mp_arg_parse_all(n_args, pos_args, kw_args, MP_ARRAY_SIZE(allowed_args), allowed_args, args);
 
     if (args[ARG_baudrate].u_int != -1) {
-        self->baudrate = args[ARG_baudrate].u_int;
+        self->delay_half = baudrate_to_delay_half(args[ARG_baudrate].u_int);
     }
     if (args[ARG_polarity].u_int != -1) {
         self->polarity = args[ARG_polarity].u_int;
@@ -86,7 +100,7 @@ mp_obj_t pyb_spi_make_new(const mp_obj_type_t *type, size_t n_args, size_t n_kw,
     mp_machine_soft_spi_obj_t *self = m_new_obj(mp_machine_soft_spi_obj_t);
     self->base.type = &pyb_spi_type;
     // set defaults
-    self->baudrate = 500000;
+    self->delay_half = baudrate_to_delay_half(500000);
     self->polarity = 0;
     self->phase = 0;
     self->sck = 14;
diff --git a/extmod/machine_spi.c b/extmod/machine_spi.c
index 3a34b7fb08..b0bd76faf9 100644
--- a/extmod/machine_spi.c
+++ b/extmod/machine_spi.c
@@ -34,8 +34,10 @@
 
 void mp_machine_soft_spi_transfer(mp_obj_base_t *self_in, size_t len, const uint8_t *src, uint8_t *dest) {
     mp_machine_soft_spi_obj_t *self = (mp_machine_soft_spi_obj_t*)self_in;
+    uint32_t delay_half = self->delay_half;
+
     // only MSB transfer is implemented
-    uint32_t delay_half = 500000 / self->baudrate + 1;
+
     for (size_t i = 0; i < len; ++i) {
         uint8_t data_out = src[i];
         uint8_t data_in = 0;
diff --git a/extmod/machine_spi.h b/extmod/machine_spi.h
index e1922c6e8b..316d06646e 100644
--- a/extmod/machine_spi.h
+++ b/extmod/machine_spi.h
@@ -37,7 +37,7 @@ typedef struct _mp_machine_spi_p_t {
 
 typedef struct _mp_machine_soft_spi_obj_t {
     mp_obj_base_t base;
-    uint32_t baudrate;
+    uint32_t delay_half; // microsecond delay for half SCK period
     uint8_t polarity;
     uint8_t phase;
     mp_hal_pin_obj_t sck;
diff --git a/stmhal/spi.c b/stmhal/spi.c
index 46da05facf..8ec6f86275 100644
--- a/stmhal/spi.c
+++ b/stmhal/spi.c
@@ -944,10 +944,23 @@ STATIC MP_DEFINE_CONST_DICT(machine_spi_locals_dict, machine_spi_locals_dict_tab
 
 /* code for soft implementation ***********************************************/
 
+STATIC uint32_t baudrate_from_delay_half(uint32_t delay_half) {
+    return 500000 / delay_half;
+}
+
+STATIC uint32_t baudrate_to_delay_half(uint32_t baudrate) {
+    uint32_t delay_half = 500000 / baudrate;
+    // round delay_half up so that: actual_baudrate <= requested_baudrate
+    if (500000 % baudrate != 0) {
+        delay_half += 1;
+    }
+    return delay_half;
+}
+
 STATIC void machine_soft_spi_print(const mp_print_t *print, mp_obj_t self_in, mp_print_kind_t kind) {
     mp_machine_soft_spi_obj_t *self = MP_OBJ_TO_PTR(self_in);
     mp_printf(print, "SPI(-1, baudrate=%u, polarity=%u, phase=%u, sck=%q, mosi=%q, miso=%q)",
-        self->baudrate, self->polarity, self->phase,
+        baudrate_from_delay_half(self->delay_half), self->polarity, self->phase,
         self->sck->name, self->mosi->name, self->miso->name);
 }
 
@@ -957,7 +970,7 @@ STATIC mp_obj_t machine_soft_spi_make_new(mp_arg_val_t *args) {
     self->base.type = &machine_soft_spi_type;
 
     // set parameters
-    self->baudrate = args[ARG_NEW_baudrate].u_int;
+    self->delay_half = baudrate_to_delay_half(args[ARG_NEW_baudrate].u_int);
     self->polarity = args[ARG_NEW_polarity].u_int;
     self->phase = args[ARG_NEW_phase].u_int;
     if (args[ARG_NEW_bits].u_int != 8) {
@@ -989,7 +1002,7 @@ STATIC void machine_soft_spi_init(mp_obj_t self_in, mp_arg_val_t *args) {
 
     // update parameters
     if (args[ARG_INIT_baudrate].u_int != -1) {
-        self->baudrate = args[ARG_INIT_baudrate].u_int;
+        self->delay_half = baudrate_to_delay_half(args[ARG_INIT_baudrate].u_int);
     }
     if (args[ARG_INIT_polarity].u_int != -1) {
         self->polarity = args[ARG_INIT_polarity].u_int;