diff --git a/scripts/mbedtls_dev/bignum_common.py b/scripts/mbedtls_dev/bignum_common.py
index 51b25a371..3bef16db6 100644
--- a/scripts/mbedtls_dev/bignum_common.py
+++ b/scripts/mbedtls_dev/bignum_common.py
@@ -19,6 +19,7 @@ import enum
 from typing import Iterator, List, Tuple, TypeVar, Any
 from copy import deepcopy
 from itertools import chain
+from math import ceil
 
 from . import test_case
 from . import test_data_generation
@@ -76,9 +77,14 @@ def combination_pairs(values: List[T]) -> List[Tuple[T, T]]:
     """Return all pair combinations from input values."""
     return [(x, y) for x in values for y in values]
 
+def bits_to_limbs(bits: int, bits_in_limb: int) -> int:
+    """ Return the appropriate ammount of limbs needed to store
+        a number contained in input bits"""
+    return ceil(bits / bits_in_limb)
+
 def hex_digits_for_limb(limbs: int, bits_in_limb: int) -> int:
-    """ Retrun the hex digits need for a number of limbs. """
-    return 2 * (limbs * bits_in_limb // 8)
+    """ Return the hex digits need for a number of limbs. """
+    return 2 * ((limbs * bits_in_limb) // 8)
 
 def hex_digits_max_int(val: str, bits_in_limb: int) -> int:
     """ Return the first number exceeding maximum  the limb space
diff --git a/scripts/mbedtls_dev/ecp.py b/scripts/mbedtls_dev/ecp.py
index 8a3ab281f..ed79a073c 100644
--- a/scripts/mbedtls_dev/ecp.py
+++ b/scripts/mbedtls_dev/ecp.py
@@ -165,7 +165,8 @@ class EcpP224R1Raw(bignum_common.ModOperationCommon,
 
     @property
     def arg_a(self) -> str:
-        hex_digits = bignum_common.hex_digits_for_limb(448 // self.bits_in_limb, self.bits_in_limb)
+        limbs = 2 * bignum_common.bits_to_limbs(224, self.bits_in_limb)
+        hex_digits = bignum_common.hex_digits_for_limb(limbs, self.bits_in_limb)
         return super().format_arg('{:x}'.format(self.int_a)).zfill(hex_digits)
 
     def result(self) -> List[str]:
@@ -624,7 +625,8 @@ class EcpP224K1Raw(bignum_common.ModOperationCommon,
 
     @property
     def arg_a(self) -> str:
-        hex_digits = bignum_common.hex_digits_for_limb(448 // self.bits_in_limb, self.bits_in_limb)
+        limbs = 2 * bignum_common.bits_to_limbs(224, self.bits_in_limb)
+        hex_digits = bignum_common.hex_digits_for_limb(limbs, self.bits_in_limb)
         return super().format_arg('{:x}'.format(self.int_a)).zfill(hex_digits)
 
     def result(self) -> List[str]: