diff --git a/bitarray/bitarray.go b/bitarray/bitarray.go
index cee0361..d2e7ec9 100644
--- a/bitarray/bitarray.go
+++ b/bitarray/bitarray.go
@@ -202,6 +202,15 @@ func (ba *bitArray) ClearBit(k uint64) error {
 	return nil
 }
 
+// Count returns the number of set bits in this array.
+func (ba *bitArray) Count() uint64 {
+	count := 0
+	for _, block := range ba.blocks {
+		count += bits.OnesCount64(uint64(block))
+	}
+	return uint64(count)
+}
+
 // Or will bitwise or two bit arrays and return a new bit array
 // representing the result.
 func (ba *bitArray) Or(other BitArray) BitArray {
diff --git a/bitarray/sparse_bitarray.go b/bitarray/sparse_bitarray.go
index 52653b0..19ec140 100644
--- a/bitarray/sparse_bitarray.go
+++ b/bitarray/sparse_bitarray.go
@@ -16,7 +16,10 @@ limitations under the License.
 
 package bitarray
 
-import "sort"
+import (
+	"math/bits"
+	"sort"
+)
 
 // uintSlice is an alias for a slice of ints.  Len, Swap, and Less
 // are exported to fulfill an interface needed for the search
@@ -243,6 +246,15 @@ func (sba *sparseBitArray) Equals(other BitArray) bool {
 	return true
 }
 
+// Count returns the number of set bits in this array.
+func (sba *sparseBitArray) Count() uint64 {
+	count := 0
+	for _, block := range sba.blocks {
+		count += bits.OnesCount64(uint64(block))
+	}
+	return uint64(count)
+}
+
 // Or will perform a bitwise or operation with the provided bitarray and
 // return a new result bitarray.
 func (sba *sparseBitArray) Or(other BitArray) BitArray {