diff --git a/src/lib.rs b/src/lib.rs
index 724798d..5707719 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -947,7 +947,7 @@ macro_rules! fixed {
                         return saturated;
                     }
                     let (neg, abs_128, overflow) =
-                        <F as SealedFloat>::to_neg_abs_overflow(val, frac_bits, int_bits);
+                        <F as SealedFloat>::to_fixed_neg_abs_overflow(val, frac_bits, int_bits);
                     if overflow {
                         return saturated;
                     }
@@ -1085,7 +1085,7 @@ macro_rules! fixed {
                         panic!("{} is not finite", val);
                     }
                     let (neg, abs_128, mut overflow) =
-                        <F as SealedFloat>::to_neg_abs_overflow(val, frac_bits, int_bits);
+                        <F as SealedFloat>::to_fixed_neg_abs_overflow(val, frac_bits, int_bits);
                     let abs_bits =
                         abs_128 as <<$Fixed<Frac> as SealedFixed>::Bits as SealedInt>::Unsigned;
 
@@ -1173,14 +1173,7 @@ macro_rules! fixed {
                 {
                     let frac_bits = Self::frac_bits();
                     let int_bits = Self::int_bits();
-                    let (neg, int, frac) = self.parts();
-                    let abs = if frac_bits == 0 {
-                        int
-                    } else if int_bits == 0 {
-                        frac
-                    } else {
-                        (int << frac_bits) | (frac >> int_bits)
-                    };
+                    let (neg, abs) = self.to_bits().neg_abs();
                     SealedFloat::from_neg_abs(neg, u128::from(abs), frac_bits, int_bits)
                 }
             }
diff --git a/src/sealed_fixed.rs b/src/sealed_fixed.rs
index b6cb283..e3ef908 100644
--- a/src/sealed_fixed.rs
+++ b/src/sealed_fixed.rs
@@ -56,6 +56,8 @@ pub trait SealedFixed: Copy {
         <Self::Bits as SealedInt>::Unsigned,
         <Self::Bits as SealedInt>::Unsigned,
     );
+
+    fn to_neg_abs_overflow(self, frac_bits: u32, int_bits: u32) -> (bool, u128, bool);
 }
 
 macro_rules! sealed_fixed {
@@ -98,6 +100,38 @@ macro_rules! sealed_fixed {
                 };
                 (neg, int_abs, frac_abs)
             }
+
+            #[inline]
+            fn to_neg_abs_overflow(
+                self,
+                dst_frac_bits: u32,
+                dst_int_bits: u32,
+            ) -> (bool, u128, bool) {
+                let src_frac_bits = <Self as SealedFixed>::frac_bits();
+                let src_bits = Self::Bits::nbits() as i32;
+                let dst_bits = (dst_frac_bits + dst_int_bits) as i32;
+
+                if SealedInt::is_zero(self.to_bits()) {
+                    return (false, 0, false);
+                }
+
+                let (neg, mut abs) = SealedInt::neg_abs(self.to_bits());
+                let leading_zeros = abs.leading_zeros();
+                abs <<= leading_zeros;
+                let need_to_shr =
+                    leading_zeros as i32 + src_frac_bits as i32 - dst_frac_bits as i32;
+                let overflow = src_bits - need_to_shr > dst_bits;
+                let abs = if need_to_shr == 0 {
+                    u128::from(abs)
+                } else if need_to_shr < 0 && -need_to_shr < 128 {
+                    u128::from(abs) << -need_to_shr
+                } else if need_to_shr > 0 && need_to_shr < 128 {
+                    u128::from(abs) >> need_to_shr
+                } else {
+                    0
+                };
+                (neg, abs, overflow)
+            }
         }
     };
 }
diff --git a/src/sealed_float.rs b/src/sealed_float.rs
index e25bf88..7d64799 100644
--- a/src/sealed_float.rs
+++ b/src/sealed_float.rs
@@ -49,7 +49,7 @@ pub trait SealedFloat: Copy + Display + Debug {
 
     fn from_neg_abs(neg: bool, abs: u128, frac_bits: u32, int_bits: u32) -> Self;
     // self must be finite, otherwise meaningless results are returned
-    fn to_neg_abs_overflow(self, frac_bits: u32, int_bits: u32) -> (bool, u128, bool);
+    fn to_fixed_neg_abs_overflow(self, frac_bits: u32, int_bits: u32) -> (bool, u128, bool);
 }
 
 macro_rules! sealed_float {
@@ -170,7 +170,11 @@ macro_rules! sealed_float {
                 Self::from_bits(bits_sign | bits_exp_mantissa)
             }
 
-            fn to_neg_abs_overflow(self, frac_bits: u32, int_bits: u32) -> (bool, u128, bool) {
+            fn to_fixed_neg_abs_overflow(
+                self,
+                frac_bits: u32,
+                int_bits: u32,
+            ) -> (bool, u128, bool) {
                 let float_bits = Self::Bits::nbits() as i32;
                 let prec = Self::prec() as i32;
                 let fix_bits = (frac_bits + int_bits) as i32;
diff --git a/src/sealed_int.rs b/src/sealed_int.rs
index a00e6f7..eb8c1b2 100644
--- a/src/sealed_int.rs
+++ b/src/sealed_int.rs
@@ -21,6 +21,9 @@ pub trait SealedInt: Copy + Ord {
     fn one_shl(shift: u32) -> Self;
     fn all_ones_shl(shift: u32) -> Self;
     fn is_zero(self) -> bool;
+
+    fn to_fixed_neg_abs_overflow(self, frac_bits: u32, int_bits: u32) -> (bool, u128, bool);
+
     fn neg_abs(self) -> (bool, Self::Unsigned);
     fn from_neg_abs(neg: bool, abs: Self::Unsigned) -> Self;
 
@@ -60,6 +63,33 @@ macro_rules! sealed_int {
                 self == 0
             }
 
+            #[inline]
+            fn to_fixed_neg_abs_overflow(
+                self,
+                frac_bits: u32,
+                int_bits: u32,
+            ) -> (bool, u128, bool) {
+                let src_bits = <Self as SealedInt>::nbits() as i32;
+                let dst_bits = (frac_bits + int_bits) as i32;
+
+                let (neg, mut abs) = SealedInt::neg_abs(self);
+                let leading_zeros = abs.leading_zeros();
+                abs <<= leading_zeros;
+                let need_to_shr =
+                    leading_zeros as i32 - frac_bits as i32;
+                let overflow = src_bits - need_to_shr > dst_bits;
+                let abs = if need_to_shr == 0 {
+                    u128::from(abs)
+                } else if need_to_shr < 0 && -need_to_shr < 128 {
+                    u128::from(abs) << -need_to_shr
+                } else if need_to_shr > 0 && need_to_shr < 128 {
+                    u128::from(abs) >> need_to_shr
+                } else {
+                    0
+                };
+                (neg, abs, overflow)
+            }
+
             $($rest)*
         }
     };
@@ -138,6 +168,22 @@ impl SealedInt for bool {
         !self
     }
 
+    #[inline]
+    fn to_fixed_neg_abs_overflow(self, frac_bits: u32, int_bits: u32) -> (bool, u128, bool) {
+        if !self {
+            return (false, 0, false);
+        }
+        let overflow = int_bits == 0;
+        let abs = if frac_bits == 0 {
+            1u128
+        } else if frac_bits < 128 {
+            1u128 << frac_bits
+        } else {
+            0
+        };
+        (false, abs, overflow)
+    }
+
     #[inline]
     fn neg_abs(self) -> (bool, bool) {
         (false, self)