diff --git a/varint.go b/varint.go
index 79ebe2f..b8b1507 100644
--- a/varint.go
+++ b/varint.go
@@ -8,12 +8,18 @@ import (
 
 // VarintSize returns the size (in bytes) of `num` encoded as a varint.
 func VarintSize(num int) int {
-	return bits.Len(uint(num))/7 + 1
+	bits := bits.Len(uint(num))
+	q, r := bits/7, bits%7
+	size := q
+	if r > 0 || size == 0 {
+		size++
+	}
+	return size
 }
 
 // CodeToVarint converts an integer to a varint-encoded []byte
 func CodeToVarint(num int) []byte {
-	buf := make([]byte, bits.Len(uint(num))/7+1)
+	buf := make([]byte, VarintSize(num))
 	n := binary.PutUvarint(buf, uint64(num))
 	return buf[:n]
 }
diff --git a/varint_test.go b/varint_test.go
new file mode 100644
index 0000000..817b3dd
--- /dev/null
+++ b/varint_test.go
@@ -0,0 +1,23 @@
+package multiaddr
+
+import (
+	"encoding/binary"
+	"testing"
+)
+
+func checkVarint(t *testing.T, x int) {
+	buf := make([]byte, binary.MaxVarintLen64)
+	expected := binary.PutUvarint(buf, uint64(x))
+
+	size := VarintSize(x)
+	if size != expected {
+		t.Fatalf("expected varintsize of %d to be %d, got %d", x, expected, size)
+	}
+}
+
+func TestVarintSize(t *testing.T) {
+	max := 1 << 16
+	for x := 0; x < max; x++ {
+		checkVarint(t, x)
+	}
+}