diff --git a/crates/utils/src/lib.cairo b/crates/utils/src/lib.cairo
index 3018850b5..e6d7fb517 100644
--- a/crates/utils/src/lib.cairo
+++ b/crates/utils/src/lib.cairo
@@ -10,7 +10,6 @@ mod fmt;
 mod helpers;
 mod i256;
 mod math;
-mod num;
 mod rlp;
 mod serialization;
 mod set;
diff --git a/crates/utils/src/math.cairo b/crates/utils/src/math.cairo
index 82113f888..55b9148ac 100644
--- a/crates/utils/src/math.cairo
+++ b/crates/utils/src/math.cairo
@@ -6,7 +6,6 @@ use integer::{
     u128_overflowing_mul, u64_wide_mul, u64_to_felt252, u32_wide_mul, u32_to_felt252, u8_wide_mul,
     u16_to_felt252
 };
-use utils::num::{SizeOf};
 
 // === Exponentiation ===
 
@@ -226,12 +225,13 @@ impl BitshiftImpl<
     +Copy<T>,
     +Drop<T>,
     +PartialOrd<T>,
-    +SizeOf<T>
+    +BitSize<T>,
+    +TryInto<usize, T>,
 > of Bitshift<T> {
     fn shl(self: T, shift: T) -> T {
         // if we shift by more than nb_bits of T, the result is 0
         // we early return to save gas and prevent unexpected behavior
-        if shift > shift.size_of() - One::one() {
+        if shift > BitSize::<T>::bits().try_into().unwrap() - One::one() {
             panic_with_felt252('mul Overflow');
         }
         let two = One::one() + One::one();
@@ -240,7 +240,7 @@ impl BitshiftImpl<
 
     fn shr(self: T, shift: T) -> T {
         // early return to save gas if shift > nb_bits of T
-        if shift > shift.size_of() - One::one() {
+        if shift > BitSize::<T>::bits().try_into().unwrap() - One::one() {
             panic_with_felt252('mul Overflow');
         }
         let two = One::one() + One::one();
@@ -272,7 +272,8 @@ impl WrappingBitshiftImpl<
     +Copy<T>,
     +OverflowingMul<T>,
     +WrappingExponentiation<T>,
-    +SizeOf<T>
+    +BitSize<T>,
+    +TryInto<usize, T>,
 > of WrappingBitshift<T> {
     fn wrapping_shl(self: T, shift: T) -> T {
         let two = One::<T>::one() + One::<T>::one();
@@ -283,7 +284,7 @@ impl WrappingBitshiftImpl<
     fn wrapping_shr(self: T, shift: T) -> T {
         let two = One::<T>::one() + One::<T>::one();
 
-        if shift > shift.size_of() - One::one() {
+        if shift > BitSize::<T>::bits().try_into().unwrap() - One::one() {
             return Zero::zero();
         }
         self / two.pow(shift)
diff --git a/crates/utils/src/num.cairo b/crates/utils/src/num.cairo
deleted file mode 100644
index 02309be27..000000000
--- a/crates/utils/src/num.cairo
+++ /dev/null
@@ -1,76 +0,0 @@
-// === SizeOf ===
-
-trait SizeOf<T> {
-    /// Returns the size in bits of Self.
-    fn size() -> T;
-    fn size_of(self: @T) -> T;
-}
-
-impl U8SizeOf of SizeOf<u8> {
-    fn size() -> u8 {
-        8
-    }
-    fn size_of(self: @u8) -> u8 {
-        U8SizeOf::size()
-    }
-}
-
-impl U16SizeOf of SizeOf<u16> {
-    fn size() -> u16 {
-        16
-    }
-    fn size_of(self: @u16) -> u16 {
-        U16SizeOf::size()
-    }
-}
-
-impl U32SizeOf of SizeOf<u32> {
-    fn size() -> u32 {
-        32
-    }
-    fn size_of(self: @u32) -> u32 {
-        U32SizeOf::size()
-    }
-}
-
-impl U64SizeOf of SizeOf<u64> {
-    fn size() -> u64 {
-        64
-    }
-    fn size_of(self: @u64) -> u64 {
-        U64SizeOf::size()
-    }
-}
-
-impl U128SizeOf of SizeOf<u128> {
-    #[inline(always)]
-    fn size() -> u128 {
-        128
-    }
-    #[inline(always)]
-    fn size_of(self: @u128) -> u128 {
-        U128SizeOf::size()
-    }
-}
-
-impl Felt252SizeOf of SizeOf<felt252> {
-    #[inline(always)]
-    fn size() -> felt252 {
-        252
-    }
-    #[inline(always)]
-    fn size_of(self: @felt252) -> felt252 {
-        Felt252SizeOf::size()
-    }
-}
-
-impl U256SizeOf of SizeOf<u256> {
-    #[inline(always)]
-    fn size() -> u256 {
-        256
-    }
-    #[inline(always)]
-    fn size_of(self: @u256) -> u256 {
-        U256SizeOf::size()
-    }
-}
diff --git a/crates/utils/src/tests.cairo b/crates/utils/src/tests.cairo
index 32610bd21..e980a6488 100644
--- a/crates/utils/src/tests.cairo
+++ b/crates/utils/src/tests.cairo
@@ -5,7 +5,6 @@ mod test_helpers;
 mod test_i256;
 mod test_math;
 mod test_modexp;
-mod test_num;
 mod test_rlp;
 mod test_serialization;
 mod test_set;
diff --git a/crates/utils/src/tests/test_num.cairo b/crates/utils/src/tests/test_num.cairo
deleted file mode 100644
index 8b2de4caf..000000000
--- a/crates/utils/src/tests/test_num.cairo
+++ /dev/null
@@ -1,17 +0,0 @@
-use utils::num::{U8SizeOf, U64SizeOf, Felt252SizeOf, SizeOf};
-
-#[test]
-fn test_sizeof() {
-    assert(10_u8.size_of() == 8, 'should be 8');
-    assert(100_u8.size_of() == 8, 'should be 8');
-    assert(20_u256.size_of() == 256, 'should be 256');
-    assert(32_felt252.size_of() == 252, 'should be 252');
-    assert(1_usize.size_of() == 32, 'should be 32');
-}
-
-#[test]
-fn test_size() {
-    assert(U8SizeOf::size() == 8, 'should be 8');
-    assert(U64SizeOf::size() == 64, 'should be 64');
-    assert(Felt252SizeOf::size() == 252, 'should be 252');
-}