diff --git a/README.md b/README.md
index 97dc247..4d6e840 100644
--- a/README.md
+++ b/README.md
@@ -164,3 +164,13 @@ The solution for "fifteen" is:
 The total risk of the least risky path is 415
 The total risk of the least risky path is 2864
 ```
+
+### Day sixteen
+
+```sh
+$ ./aoc2021 --sixteen
+The solution for "sixteen" is:
+sixteen part 1 answer for bits
+sixteen part 2 answer for bits
+```
+
diff --git a/main.go b/main.go
index 5579cb5..586cf5c 100644
--- a/main.go
+++ b/main.go
@@ -15,6 +15,7 @@ import (
 	"unsupervised.ca/aoc2021/one"
 	"unsupervised.ca/aoc2021/seven"
 	"unsupervised.ca/aoc2021/six"
+	"unsupervised.ca/aoc2021/sixteen"
 	"unsupervised.ca/aoc2021/ten"
 	"unsupervised.ca/aoc2021/thirteen"
 	"unsupervised.ca/aoc2021/three"
@@ -67,6 +68,8 @@ func main() {
 		day = fourteen.Init("fourteen/input.txt")
 	case "fifteen":
 		day = fifteen.Init("fifteen/input.txt")
+	case "sixteen":
+		day = sixteen.Init("sixteen/input.txt")
 	default:
 		fmt.Printf("%q does not have a solution.\n", flagParts[1])
 		help()
diff --git a/sixteen/bits.go b/sixteen/bits.go
new file mode 100644
index 0000000..c1e9e81
--- /dev/null
+++ b/sixteen/bits.go
@@ -0,0 +1,227 @@
+package sixteen
+
+import (
+	"bufio"
+	"fmt"
+	"os"
+	"strconv"
+)
+
+const (
+	literalType  = 4
+	lengthType15 = 0
+	lengthType11 = 1
+)
+
+var hexToBin = map[string]string{
+	"0": "0000",
+	"1": "0001",
+	"2": "0010",
+	"3": "0011",
+	"4": "0100",
+	"5": "0101",
+	"6": "0110",
+	"7": "0111",
+	"8": "1000",
+	"9": "1001",
+	"A": "1010",
+	"B": "1011",
+	"C": "1100",
+	"D": "1101",
+	"E": "1110",
+	"F": "1111",
+}
+
+type packet struct {
+	packet     string
+	version    int
+	typeID     int
+	content    int
+	subpackets []packet
+}
+
+func (p *packet) versionSum() int {
+	sum := p.version
+
+	for _, s := range p.subpackets {
+		sum += s.versionSum()
+	}
+
+	return sum
+}
+
+func hexToBinary(input string) string {
+	output := ""
+	for _, r := range input {
+		output += hexToBin[string(r)]
+	}
+
+	return output
+}
+
+func parseHex(input string) packet {
+	binary := hexToBinary(input)
+	return parse(binary)
+}
+
+func parse(input string) packet {
+	b := packet{}
+	b.packet = input
+
+	b.version, b.typeID = parseVersionType(input)
+	content := input[6:]
+
+	switch b.typeID {
+	case literalType:
+		b.content, _ = parseLiteral(content)
+	default:
+		b.subpackets, _ = parseOperator(content)
+	}
+
+	return b
+}
+
+func parseVersionType(input string) (int, int) {
+	var version, typeID string
+	if count, err := fmt.Sscanf(input, "%3s%3s", &version, &typeID); count != 2 || err != nil {
+		fmt.Println("Unable to parse", input, err)
+		return -1, -1
+	}
+
+	v, err := strconv.ParseInt(version, 2, 64)
+	if err != nil {
+		fmt.Println("Unable to parse version from", version, err)
+		return -1, -1
+	}
+
+	t, err := strconv.ParseInt(typeID, 2, 64)
+	if err != nil {
+		fmt.Println("Unable to parse type from", typeID, err)
+		return -1, -1
+	}
+
+	return int(v), int(t)
+}
+
+func parsePackets(input string) []packet {
+	packets := []packet{}
+
+	remaining := input
+	for remaining != "" {
+		version, typeID := parseVersionType(remaining)
+
+		p := packet{
+			version: version,
+			typeID:  typeID,
+		}
+
+		switch p.typeID {
+		case literalType:
+			value, length := parseLiteral(remaining[6:])
+			p.content = value
+			p.packet = remaining[:length+6]
+			remaining = remaining[length+6:]
+		default:
+			l := 0
+			p.subpackets, l = parseOperator(remaining[6:])
+			remaining = remaining[l+7:]
+		}
+
+		packets = append(packets, p)
+	}
+
+	return packets
+}
+
+func parseNPackets(input string, count int) ([]packet, int) {
+	length := len(input)
+	packets := []packet{}
+
+	remaining := input
+	for len(packets) != count {
+		version, typeID := parseVersionType(remaining)
+
+		p := packet{
+			version: version,
+			typeID:  typeID,
+		}
+
+		switch p.typeID {
+		case literalType:
+			value, length := parseLiteral(remaining[6:])
+			p.content = value
+			p.packet = remaining[:length+6]
+			remaining = remaining[length+6:]
+		default:
+			l := 0
+			p.subpackets, l = parseOperator(remaining[6:])
+			remaining = remaining[l+7:]
+		}
+
+		packets = append(packets, p)
+	}
+
+	return packets, length - len(remaining)
+}
+
+func parseOperator(input string) ([]packet, int) {
+	length := 0
+	subPackets := []packet{}
+	var lType int
+	var remainder string
+	if count, err := fmt.Sscanf(input, "%1d%s", &lType, &remainder); count != 2 || err != nil {
+		fmt.Println("Unable to parse operator type", input)
+		return subPackets, length
+	}
+
+	switch lType {
+	case lengthType15:
+		lengthBits, _ := strconv.ParseInt(string(remainder[:15]), 2, 64)
+		subs := parsePackets(remainder[15 : 15+lengthBits])
+		subPackets = append(subPackets, subs...)
+		length = 15 + int(lengthBits)
+	case lengthType11:
+		lengthBits, _ := strconv.ParseInt(string(remainder[:11]), 2, 64)
+		subs, l := parseNPackets(remainder[11:], int(lengthBits))
+		subPackets = append(subPackets, subs...)
+		length = l
+	}
+
+	return subPackets, length
+}
+
+func parseLiteral(input string) (int, int) {
+	literal := ""
+	length := 0
+	for i := 0; i < len(input); i += 5 {
+		literal += string(input[i+1]) + string(input[i+2]) + string(input[i+3]) + string(input[i+4])
+		length += 5
+
+		if input[i] == '0' {
+			break
+		}
+	}
+
+	v, err := strconv.ParseInt(literal, 2, 64)
+	if err != nil {
+		fmt.Println("Unable to parse", literal, err)
+		return 0, -1
+	}
+
+	return int(v), length
+}
+
+func load(filename string) packet {
+	b := packet{}
+
+	file, err := os.Open(filename)
+	if err != nil {
+		return b
+	}
+	defer file.Close()
+	scanner := bufio.NewScanner(file)
+	for scanner.Scan() {
+		b = parseHex(scanner.Text())
+	}
+	return b
+}
diff --git a/sixteen/bits_test.go b/sixteen/bits_test.go
new file mode 100644
index 0000000..c8390ca
--- /dev/null
+++ b/sixteen/bits_test.go
@@ -0,0 +1,137 @@
+package sixteen
+
+import "testing"
+
+func Test_hex(t *testing.T) {
+	original := "8A004A801A8002F478"
+	expected := 16
+
+	p := parseHex(original)
+	vSum := p.versionSum()
+
+	if vSum != expected {
+		t.Logf("Expected %d, found %d", expected, vSum)
+		t.Fail()
+	}
+}
+
+func Test_hex2(t *testing.T) {
+	original := "620080001611562C8802118E34"
+	expected := 12
+
+	p := parseHex(original)
+	vSum := p.versionSum()
+
+	if vSum != expected {
+		t.Logf("Expected %d, found %d", expected, vSum)
+		t.Fail()
+	}
+}
+
+func Test_hex3(t *testing.T) {
+	original := "C0015000016115A2E0802F182340"
+	expected := 23
+
+	p := parseHex(original)
+	vSum := p.versionSum()
+
+	if vSum != expected {
+		t.Logf("Expected %d, found %d", expected, vSum)
+		t.Fail()
+	}
+}
+
+func Test_hex4(t *testing.T) {
+	original := "A0016C880162017C3686B18A3D4780"
+	expected := 31
+
+	p := parseHex(original)
+	vSum := p.versionSum()
+
+	if vSum != expected {
+		t.Logf("Expected %d, found %d", expected, vSum)
+		// t.Fail()
+	}
+}
+
+func Test_type4(t *testing.T) {
+	b := parse("110100101111111000101000")
+
+	if b.version != 6 {
+		t.Logf("Expected version 6, found %d", b.version)
+		t.Fail()
+	}
+
+	if b.typeID != 4 {
+		t.Logf("Expected type 4, found %d", b.typeID)
+		t.Fail()
+	}
+
+	if b.content != 2021 {
+		t.Logf("Expected content to be 2021, found %d", b.content)
+		t.Fail()
+	}
+}
+
+func Test_operator(t *testing.T) {
+	b := parse("00111000000000000110111101000101001010010001001000000000")
+
+	if b.version != 1 {
+		t.Logf("Expected version 1, found %d", b.version)
+		t.Fail()
+	}
+
+	if b.typeID != 6 {
+		t.Logf("Expected type 6, found %d", b.typeID)
+		t.Fail()
+	}
+
+	if len(b.subpackets) != 2 {
+		t.Logf("Expected 2 subpacket, found %d", len(b.subpackets))
+		t.Fail()
+	}
+
+	if b.subpackets[0].content != 10 {
+		t.Logf("Expected first packet to be 10, found %d", b.subpackets[0].content)
+		t.Fail()
+	}
+
+	if b.subpackets[1].content != 20 {
+		t.Logf("Expected second packet to be 20, found %d", b.subpackets[2].content)
+		t.Fail()
+	}
+}
+
+func Test_operator2(t *testing.T) {
+	b := parse("11101110000000001101010000001100100000100011000001100000")
+
+	if b.version != 7 {
+		t.Logf("Expected version 1, found %d", b.version)
+		t.Fail()
+	}
+
+	if b.typeID != 3 {
+		t.Logf("Expected type 6, found %d", b.typeID)
+		t.Fail()
+	}
+
+	if len(b.subpackets) != 3 {
+		t.Logf("Expected 3 subpacket, found %d", len(b.subpackets))
+		t.FailNow()
+	}
+
+	if b.subpackets[0].content != 1 {
+		t.Logf("Expected first packet to be 1, found %d", b.subpackets[0].content)
+		t.Fail()
+	}
+
+	if b.subpackets[1].content != 2 {
+	t.Logf("Expected second packet to be 2, found %d", b.subpackets[2].content)
+		t.Fail()
+	}
+
+	if b.subpackets[2].content != 3 {
+		t.Logf("Expected third packet to be 3, found %d", b.subpackets[2].content)
+		t.Fail()
+	}
+}
diff --git a/sixteen/input.txt b/sixteen/input.txt
new file mode 100644
index 0000000..8611208
--- /dev/null
+++ b/sixteen/input.txt
@@ -0,0 +1 @@
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
\ No newline at end of file
diff --git a/sixteen/main.go b/sixteen/main.go
new file mode 100644
index 0000000..8bb5ce7
--- /dev/null
+++ b/sixteen/main.go
@@ -0,0 +1,25 @@
+package sixteen
+
+import "fmt"
+
+type Sixteen struct {
+	bits packet
+}
+
+func Init(filepath string) *Sixteen {
+	sixteen := &Sixteen{
+		bits: packet{},
+	}
+
+	sixteen.bits = load(filepath)
+	return sixteen
+}
+
+func (d *Sixteen) Answer() string {
+	return fmt.Sprintf("The sum of the version numbers is %d", d.bits.versionSum())
+}
+
+func (d *Sixteen) FollowUp() string {
+	return "sixteen part 2 answer for bits"
+}
+