diff --git a/pkg/gravatar/gravatar.go b/pkg/gravatar/gravatar.go
new file mode 100644
index 00000000..a1d02ed4
--- /dev/null
+++ b/pkg/gravatar/gravatar.go
@@ -0,0 +1,34 @@
+package gravatar
+
+import (
+	"crypto/md5"
+	"encoding/hex"
+	"fmt"
+	"net/url"
+)
+
+const (
+	defaultURLPrefix = "https://www.gravatar.com/avatar/"
+)
+
+// GetAvatarURL get avatar url from gravatar by email
+func GetAvatarURL(email string) string {
+	h := md5.New()
+	h.Write([]byte(email))
+	return defaultURLPrefix + hex.EncodeToString(h.Sum(nil))
+}
+
+// Resize resize avatar by pixel
+func Resize(originalAvatarURL string, sizePixel int) (resizedAvatarURL string) {
+	if len(originalAvatarURL) == 0 {
+		return
+	}
+	originalURL, err := url.Parse(originalAvatarURL)
+	if err != nil {
+		return originalAvatarURL
+	}
+	query := originalURL.Query()
+	query.Set("p", fmt.Sprintf("%d", sizePixel))
+	originalURL.RawQuery = query.Encode()
+	return originalURL.String()
+}
diff --git a/pkg/gravatar/gravatar_test.go b/pkg/gravatar/gravatar_test.go
new file mode 100644
index 00000000..98928b1a
--- /dev/null
+++ b/pkg/gravatar/gravatar_test.go
@@ -0,0 +1,71 @@
+package gravatar
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestGetAvatarURL(t *testing.T) {
+	type args struct {
+		email string
+	}
+	tests := []struct {
+		name string
+		args args
+		want string
+	}{
+		{
+			name: "answer@answer.com",
+			args: args{email: "answer@answer.com"},
+			want: "https://www.gravatar.com/avatar/b2be4e4438f08a5e885be8de5f41fdd7",
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			assert.Equal(t, tt.want, GetAvatarURL(tt.args.email))
+		})
+	}
+}
+
+func TestResize(t *testing.T) {
+	type args struct {
+		originalAvatarURL string
+		sizePixel         int
+	}
+	tests := []struct {
+		name                 string
+		args                 args
+		wantResizedAvatarURL string
+	}{
+		{
+			name: "original url",
+			args: args{
+				originalAvatarURL: "https://www.gravatar.com/avatar/b2be4e4438f08a5e885be8de5f41fdd7",
+				sizePixel:         128,
+			},
+			wantResizedAvatarURL: "https://www.gravatar.com/avatar/b2be4e4438f08a5e885be8de5f41fdd7?p=128",
+		},
+		{
+			name: "already resized url",
+			args: args{
+				originalAvatarURL: "https://www.gravatar.com/avatar/b2be4e4438f08a5e885be8de5f41fdd7?p=128",
+				sizePixel:         64,
+			},
+			wantResizedAvatarURL: "https://www.gravatar.com/avatar/b2be4e4438f08a5e885be8de5f41fdd7?p=64",
+		},
+		{
+			name: "empty url",
+			args: args{
+				originalAvatarURL: "",
+				sizePixel:         64,
+			},
+			wantResizedAvatarURL: "",
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			assert.Equalf(t, tt.wantResizedAvatarURL, Resize(tt.args.originalAvatarURL, tt.args.sizePixel), "Resize(%v, %v)", tt.args.originalAvatarURL, tt.args.sizePixel)
+		})
+	}
+}