diff --git a/sqlite-vec.c b/sqlite-vec.c
index 3cc802f0..b4412fa9 100644
--- a/sqlite-vec.c
+++ b/sqlite-vec.c
@@ -460,6 +460,58 @@ static double distance_l1_f32(const void *a, const void *b, const void *d) {
   return l1_f32(a, b, d);
 }
 
+// https://github.com/facebookresearch/faiss/blob/77e2e79cd0a680adc343b9840dd865da724c579e/faiss/utils/hamming_distance/common.h#L34
+static u8 hamdist_table[256] = {
+  0, 1, 1, 2, 1, 2, 2, 3, 1, 2, 2, 3, 2, 3, 3, 4, 1, 2, 2, 3, 2, 3, 3, 4,
+  2, 3, 3, 4, 3, 4, 4, 5, 1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5,
+  2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6, 1, 2, 2, 3, 2, 3, 3, 4,
+  2, 3, 3, 4, 3, 4, 4, 5, 2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
+  2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6, 3, 4, 4, 5, 4, 5, 5, 6,
+  4, 5, 5, 6, 5, 6, 6, 7, 1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5,
+  2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6, 2, 3, 3, 4, 3, 4, 4, 5,
+  3, 4, 4, 5, 4, 5, 5, 6, 3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7,
+  2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6, 3, 4, 4, 5, 4, 5, 5, 6,
+  4, 5, 5, 6, 5, 6, 6, 7, 3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7,
+  4, 5, 5, 6, 5, 6, 6, 7, 5, 6, 6, 7, 6, 7, 7, 8};
+
+static f32 distance_cosine_bit_u64(u64 *a, u64 *b, size_t n) {
+  f32 dot = 0;
+  f32 aMag = 0;
+  f32 bMag = 0;
+
+  for (size_t i = 0; i < n; i++) {
+    dot += __builtin_popcountl(a[i] & b[i]);
+    aMag += __builtin_popcountl(a[i]);
+    bMag += __builtin_popcountl(b[i]);
+  }
+
+  return 1 - (dot / (sqrt(aMag) * sqrt(bMag)));
+}
+
+static f32 distance_cosine_bit_u8(u8 *a, u8 *b, size_t n) {
+  f32 dot = 0;
+  f32 aMag = 0;
+  f32 bMag = 0;
+
+  for (size_t i = 0; i < n; i++) {
+    dot += hamdist_table[a[i] & b[i]];
+    aMag += hamdist_table[a[i]];
+    bMag += hamdist_table[b[i]];
+  }
+
+  return 1 - (dot / (sqrt(aMag) * sqrt(bMag)));
+}
+
+static f32 distance_cosine_bit(const void *pA, const void *pB,
+                               const void *pD) {
+  size_t dim = *((size_t *)pD);
+
+  if ((dim % 64) == 0) {
+    return distance_cosine_bit_u64((u64 *)pA, (u64 *)pB, dim / 8 / CHAR_BIT);
+  }
+  return distance_cosine_bit_u8((u8 *)pA, (u8 *)pB, dim / CHAR_BIT);
+}
+
 static f32 distance_cosine_float(const void *pVect1v, const void *pVect2v,
                                  const void *qty_ptr) {
   f32 *pVect1 = (f32 *)pVect1v;
@@ -497,20 +549,6 @@ static f32 distance_cosine_int8(const void *pA, const void *pB,
   return 1 - (dot / (sqrt(aMag) * sqrt(bMag)));
 }
 
-// https://github.com/facebookresearch/faiss/blob/77e2e79cd0a680adc343b9840dd865da724c579e/faiss/utils/hamming_distance/common.h#L34
-static u8 hamdist_table[256] = {
-    0, 1, 1, 2, 1, 2, 2, 3, 1, 2, 2, 3, 2, 3, 3, 4, 1, 2, 2, 3, 2, 3, 3, 4,
-    2, 3, 3, 4, 3, 4, 4, 5, 1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5,
-    2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6, 1, 2, 2, 3, 2, 3, 3, 4,
-    2, 3, 3, 4, 3, 4, 4, 5, 2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
-    2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6, 3, 4, 4, 5, 4, 5, 5, 6,
-    4, 5, 5, 6, 5, 6, 6, 7, 1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5,
-    2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6, 2, 3, 3, 4, 3, 4, 4, 5,
-    3, 4, 4, 5, 4, 5, 5, 6, 3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7,
-    2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6, 3, 4, 4, 5, 4, 5, 5, 6,
-    4, 5, 5, 6, 5, 6, 6, 7, 3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7,
-    4, 5, 5, 6, 5, 6, 6, 7, 5, 6, 6, 7, 6, 7, 7, 8};
-
 static f32 distance_hamming_u8(u8 *a, u8 *b, size_t n) {
   int same = 0;
   for (unsigned long i = 0; i < n; i++) {
@@ -1167,9 +1205,8 @@ static void vec_distance_cosine(sqlite3_context *context, int argc,
 
   switch (elementType) {
   case SQLITE_VEC_ELEMENT_TYPE_BIT: {
-    sqlite3_result_error(
-        context, "Cannot calculate cosine distance between two bitvectors.",
-        -1);
+    f32 result = distance_cosine_bit(a, b, &dimensions);
+    sqlite3_result_double(context, result);
     goto finish;
   }
   case SQLITE_VEC_ELEMENT_TYPE_FLOAT32: {
diff --git a/tests/test-loadable.py b/tests/test-loadable.py
index a8058c9e..38618f08 100644
--- a/tests/test-loadable.py
+++ b/tests/test-loadable.py
@@ -423,6 +423,25 @@ def check(a, b, dtype=np.float32):
     check([1, 2, 3], [-9, -8, -7], dtype=np.int8)
     assert vec_distance_cosine("[1.1, 1.0]", "[1.2, 1.2]") == 0.001131898257881403
 
+    vec_distance_cosine_bit = lambda *args: db.execute(
+        "select vec_distance_cosine(vec_bit(?), vec_bit(?))", args
+    ).fetchone()[0]
+    assert isclose(
+        vec_distance_cosine_bit(b"\xff", b"\x01"),
+        npy_cosine([1,1,1,1,1,1,1,1], [0,0,0,0,0,0,0,1]),
+        abs_tol=1e-6
+    )
+    assert isclose(
+        vec_distance_cosine_bit(b"\xab", b"\xab"),
+        npy_cosine([1,0,1,0,1,0,1,1], [1,0,1,0,1,0,1,1]),
+        abs_tol=1e-6
+    )
+    # test 64-bit
+    assert isclose(
+        vec_distance_cosine_bit(b"\xaa" * 8, b"\xff" * 8),
+        npy_cosine([1,0] * 32, [1] * 64),
+        abs_tol=1e-6
+    )
 
 def test_vec_distance_hamming():
     vec_distance_hamming = lambda *args: db.execute(