diff --git a/17_number_letter_count/main.go b/17_number_letter_count/main.go
new file mode 100644
index 0000000..ea35d4e
--- /dev/null
+++ b/17_number_letter_count/main.go
@@ -0,0 +1,78 @@
+package main
+
+import "fmt"
+
+func main() {
+	count := 0
+	for i := 1; i <= 1000; i++ {
+		count += CountNumberLetter(i)
+	}
+	fmt.Println("count:", count)
+}
+
+var numberToLetter = map[int]string{
+	1:    "one",
+	2:    "two",
+	3:    "three",
+	4:    "four",
+	5:    "five",
+	6:    "six",
+	7:    "seven",
+	8:    "eight",
+	9:    "nine",
+	10:   "ten",
+	11:   "eleven",
+	12:   "twelve",
+	13:   "thirteen",
+	14:   "fourteen",
+	15:   "fifteen",
+	16:   "sixteen",
+	17:   "seventeen",
+	18:   "eighteen",
+	19:   "nineteen",
+	20:   "twenty",
+	30:   "thirty",
+	40:   "forty",
+	50:   "fifty",
+	60:   "sixty",
+	70:   "seventy",
+	80:   "eighty",
+	90:   "ninety",
+	100:  "hundred",
+	1000: "thousand",
+}
+
+func CountNumberLetter(input int) int {
+	n := input
+	num := ""
+	if input <= 20 {
+		num += numberToLetter[input]
+		fmt.Println("input:", n, "num:", num, len(num))
+		return len(num)
+	}
+	if input/1000 > 0 {
+		num += "onethousand"
+		input = input % 1000
+	}
+	hundred := input / 100
+	if hundred != 0 {
+		num += numberToLetter[hundred] + "hundred"
+	}
+	input = input % 100
+	one := input % 10
+	ten := input / 10
+	if one == 0 && hundred == 0 {
+		num += numberToLetter[input]
+	} else {
+		if hundred > 0 && (one > 0 || ten > 0) {
+			num += "and"
+		}
+		if ten == 1 {
+			num += numberToLetter[input]
+		} else {
+			num += numberToLetter[ten*10] + numberToLetter[one]
+		}
+	}
+	fmt.Println("input:", n, "num:", num, "len:", len(num))
+	return len(num)
+}
diff --git a/17_number_letter_count/number_letter_count_test.go b/17_number_letter_count/number_letter_count_test.go
new file mode 100644
index 0000000..d03628b
--- /dev/null
+++ b/17_number_letter_count/number_letter_count_test.go
@@ -0,0 +1,93 @@
+package main
+
+import (
+	"testing"
+)
+
+func TestCountNumberLetter(t *testing.T) {
+	tt := []struct {
+		name  string
+		input int
+		want  int
+	}{
+		{
+			"1",
+			1,
+			3,
+		},
+		{
+			"15",
+			15,
+			7,
+		},
+		{
+			"90",
+			90,
+			6,
+		},
+		{
+			"100",
+			100,
+			10,
+		},
+		{
+			"300",
+			300,
+			12,
+		},
+		{
+			"23",
+			23,
+			11,
+		},
+		{
+			"123",
+			123,
+			24,
+		},
+		{
+			"120",
+			120,
+			19,
+		},
+		{
+			"115",
+			115,
+			20,
+		},
+		{
+			"320",
+			320,
+			21,
+		},
+		{
+			"444",
+			444,
+			23,
+		},
+		{
+			"499",
+			499,
+			24,
+		},
+		{
+			"342",
+			342,
+			23,
+		},
+		{
+			"110",
+			110,
+			16,
+		},
+	}
+
+	for _, tc := range tt {
+		t.Run(tc.name, func(t *testing.T) {
+			got := CountNumberLetter(tc.input)
+			if got != tc.want {
+				t.Errorf("CountNumberLetter(%d)=%d, want %d", tc.input, got, tc.want)
+			}
+		})
+	}
+}