diff --git a/drivers/at25xxx/at25xxx.c b/drivers/at25xxx/at25xxx.c
index 33509b9cf0..b2b3d59e53 100644
--- a/drivers/at25xxx/at25xxx.c
+++ b/drivers/at25xxx/at25xxx.c
@@ -113,7 +113,7 @@ static ssize_t _write_page(const at25xxx_t *dev, uint32_t pos, const void *data,
 
 int at25xxx_write(const at25xxx_t *dev, uint32_t pos, const void *data, size_t len)
 {
-    int res = 0;
+    int res = len;
     const uint8_t *d = data;
 
     if (pos + len > dev->params.size) {
@@ -164,7 +164,7 @@ int at25xxx_read(const at25xxx_t *dev, uint32_t pos, void *data, size_t len)
 
     spi_release(dev->params.spi);
 
-    return 0;
+    return len;
 }
 
 uint8_t at25xxx_read_byte(const at25xxx_t *dev, uint32_t pos)
diff --git a/drivers/include/at25xxx.h b/drivers/include/at25xxx.h
index e4bd598234..33502bd5af 100644
--- a/drivers/include/at25xxx.h
+++ b/drivers/include/at25xxx.h
@@ -82,7 +82,7 @@ uint8_t at25xxx_read_byte(const at25xxx_t *dev, uint32_t pos);
  * @param[out] data     read buffer
  * @param[in] len       requested length to be read
  *
- * @return    0 on success
+ * @return    Number of bytes read
  * @return    -ERANGE if pos + len > EEPROM size
  */
 int at25xxx_read(const at25xxx_t *dev, uint32_t pos, void *data, size_t len);
@@ -104,7 +104,7 @@ void at25xxx_write_byte(const at25xxx_t *dev, uint32_t pos, uint8_t data);
  * @param[in] data      write buffer
  * @param[in] len       requested length to be written
  *
- * @return    0 on success
+ * @return    Number of bytes written
  * @return    -ERANGE if pos + len > EEPROM size
  */
 int at25xxx_write(const at25xxx_t *dev, uint32_t pos, const void *data, size_t len);
diff --git a/tests/driver_at25xxx/main.c b/tests/driver_at25xxx/main.c
index b4f1ebeff0..a148edff92 100644
--- a/tests/driver_at25xxx/main.c
+++ b/tests/driver_at25xxx/main.c
@@ -34,12 +34,12 @@ static void test_normal_write(void)
     const char data_in_b[] = "This is a test.";
     char data_out[32];
 
-    TEST_ASSERT_EQUAL_INT(0, at25xxx_write(&dev, 0, data_in_a, sizeof(data_in_a)));
-    TEST_ASSERT_EQUAL_INT(0, at25xxx_read(&dev, 0, data_out, sizeof(data_out)));
+    TEST_ASSERT_EQUAL_INT(sizeof(data_in_a), at25xxx_write(&dev, 0, data_in_a, sizeof(data_in_a)));
+    TEST_ASSERT_EQUAL_INT(sizeof(data_out), at25xxx_read(&dev, 0, data_out, sizeof(data_out)));
     TEST_ASSERT_EQUAL_STRING(data_in_a, data_out);
 
-    TEST_ASSERT_EQUAL_INT(0, at25xxx_write(&dev, 0, data_in_b, sizeof(data_in_b)));
-    TEST_ASSERT_EQUAL_INT(0, at25xxx_read(&dev, 0, data_out, sizeof(data_out)));
+    TEST_ASSERT_EQUAL_INT(sizeof(data_in_b), at25xxx_write(&dev, 0, data_in_b, sizeof(data_in_b)));
+    TEST_ASSERT_EQUAL_INT(sizeof(data_out), at25xxx_read(&dev, 0, data_out, sizeof(data_out)));
     TEST_ASSERT_EQUAL_STRING(data_in_b, data_out);
 }
 
@@ -49,12 +49,16 @@ static void test_page_write(void)
     const char data_in_b[] = "This is a test.";
     char data_out[32];
 
-    TEST_ASSERT_EQUAL_INT(0, at25xxx_write(&dev, AT25XXX_PARAM_PAGE_SIZE - 5, data_in_a, sizeof(data_in_a)));
-    TEST_ASSERT_EQUAL_INT(0, at25xxx_read(&dev, AT25XXX_PARAM_PAGE_SIZE - 5, data_out, sizeof(data_out)));
+    TEST_ASSERT_EQUAL_INT(sizeof(data_in_a),
+                          at25xxx_write(&dev, AT25XXX_PARAM_PAGE_SIZE - 5, data_in_a, sizeof(data_in_a)));
+    TEST_ASSERT_EQUAL_INT(sizeof(data_out),
+                          at25xxx_read(&dev, AT25XXX_PARAM_PAGE_SIZE - 5, data_out, sizeof(data_out)));
     TEST_ASSERT_EQUAL_STRING(data_in_a, data_out);
 
-    TEST_ASSERT_EQUAL_INT(0, at25xxx_write(&dev, AT25XXX_PARAM_PAGE_SIZE - 5, data_in_b, sizeof(data_in_b)));
-    TEST_ASSERT_EQUAL_INT(0, at25xxx_read(&dev, AT25XXX_PARAM_PAGE_SIZE - 5, data_out, sizeof(data_out)));
+    TEST_ASSERT_EQUAL_INT(sizeof(data_in_b),
+                          at25xxx_write(&dev, AT25XXX_PARAM_PAGE_SIZE - 5, data_in_b, sizeof(data_in_b)));
+    TEST_ASSERT_EQUAL_INT(sizeof(data_out),
+                          at25xxx_read(&dev, AT25XXX_PARAM_PAGE_SIZE - 5, data_out, sizeof(data_out)));
     TEST_ASSERT_EQUAL_STRING(data_in_b, data_out);
 }
 
@@ -66,12 +70,15 @@ static void test_page_clear(void)
 
     memset(data_clr, 0, sizeof(data_clr));
 
-    TEST_ASSERT_EQUAL_INT(0, at25xxx_write(&dev, AT25XXX_PARAM_PAGE_SIZE - 5, data_in_a, sizeof(data_in_a)));
-    TEST_ASSERT_EQUAL_INT(0, at25xxx_read(&dev, AT25XXX_PARAM_PAGE_SIZE - 5, data_out, sizeof(data_out)));
+    TEST_ASSERT_EQUAL_INT(sizeof(data_in_a),
+                          at25xxx_write(&dev, AT25XXX_PARAM_PAGE_SIZE - 5, data_in_a, sizeof(data_in_a)));
+    TEST_ASSERT_EQUAL_INT(sizeof(data_out),
+                          at25xxx_read(&dev, AT25XXX_PARAM_PAGE_SIZE - 5, data_out, sizeof(data_out)));
     TEST_ASSERT_EQUAL_STRING(data_in_a, data_out);
 
     TEST_ASSERT_EQUAL_INT(0, at25xxx_clear(&dev, AT25XXX_PARAM_PAGE_SIZE - 5, sizeof(data_out)));
-    TEST_ASSERT_EQUAL_INT(0, at25xxx_read(&dev, AT25XXX_PARAM_PAGE_SIZE - 5, data_out, sizeof(data_out)));
+    TEST_ASSERT_EQUAL_INT(sizeof(data_out),
+                          at25xxx_read(&dev, AT25XXX_PARAM_PAGE_SIZE - 5, data_out, sizeof(data_out)));
     TEST_ASSERT_EQUAL_INT(0, memcmp(data_out, data_clr, sizeof(data_clr)));
 }