diff --git a/README.md b/README.md
index 6a263a8..99fe924 100644
--- a/README.md
+++ b/README.md
@@ -1,2 +1,5 @@
 # crc16
 
+An CRC-16 implementation
+
+Made with this https://www.sunshine2k.de/articles/coding/crc/understanding_crc.html#ch4 tutorial.
\ No newline at end of file
diff --git a/crc.go b/crc.go
new file mode 100644
index 0000000..b325db5
--- /dev/null
+++ b/crc.go
@@ -0,0 +1,32 @@
+package crc16
+
+var Crc16Table = make([]uint16, 256)
+
+const GeneratorPolynomial = 0x1021
+
+func init() {
+	calculateTable()
+}
+
+func calculateTable() {
+	for dividend := 0; dividend < 256; dividend++ {
+		crc := uint16(dividend << 8)
+		for bit := 0; bit < 8; bit++ {
+			if (crc & 0x8000) != 0 {
+				crc = (crc << 1) ^ GeneratorPolynomial
+			} else {
+				crc <<= 1
+			}
+		}
+		Crc16Table[dividend] = crc
+	}
+}
+
+func Calculate(data []byte) uint16 {
+	crc := uint16(0)
+	for _, b := range data {
+		pos := byte(crc>>8) ^ b
+		crc = (crc << 8) ^ Crc16Table[pos]
+	}
+	return crc
+}
diff --git a/go.mod b/go.mod
new file mode 100644
index 0000000..66de3f3
--- /dev/null
+++ b/go.mod
@@ -0,0 +1,3 @@
+module git.barfuss.email/jan/crc16
+
+go 1.22.1