diff --git a/ident.go b/ident.go
index 78b51d4..da3560b 100644
--- a/ident.go
+++ b/ident.go
@@ -38,9 +38,9 @@ func toParts(s string) []string {
 		return []string{strings.ToUpper(s)}
 	}
 	var prev rune
-	var x string
+	var x strings.Builder
+	x.Grow(len(s))
 	for _, c := range s {
-		cs := string(c)
 		// fmt.Println("### cs ->", cs)
 		// fmt.Println("### unicode.IsControl(c) ->", unicode.IsControl(c))
 		// fmt.Println("### unicode.IsDigit(c) ->", unicode.IsDigit(c))
@@ -58,35 +58,38 @@ func toParts(s string) []string {
 		}
 
 		if isSpace(c) {
-			parts = xappend(parts, x)
-			x = cs
+			parts = xappend(parts, x.String())
+			x.Reset()
+			x.WriteRune(c)
 			prev = c
 			continue
 		}
 
 		if unicode.IsUpper(c) && !unicode.IsUpper(prev) {
-			parts = xappend(parts, x)
-			x = cs
+			parts = xappend(parts, x.String())
+			x.Reset()
+			x.WriteRune(c)
 			prev = c
 			continue
 		}
-		if unicode.IsUpper(c) && baseAcronyms[strings.ToUpper(x)] {
-			parts = xappend(parts, x)
-			x = cs
+		if unicode.IsUpper(c) && baseAcronyms[strings.ToUpper(x.String())] {
+			parts = xappend(parts, x.String())
+			x.Reset()
+			x.WriteRune(c)
 			prev = c
 			continue
 		}
 		if unicode.IsLetter(c) || unicode.IsDigit(c) || unicode.IsPunct(c) || c == '`' {
 			prev = c
-			x += cs
+			x.WriteRune(c)
 			continue
 		}
 
-		parts = xappend(parts, x)
-		x = ""
+		parts = xappend(parts, x.String())
+		x.Reset()
 		prev = c
 	}
-	parts = xappend(parts, x)
+	parts = xappend(parts, x.String())
 
 	return parts
 }
diff --git a/ident_test.go b/ident_test.go
index 034acb0..3994d29 100644
--- a/ident_test.go
+++ b/ident_test.go
@@ -64,3 +64,49 @@ func Test_MarshalText(t *testing.T) {
 	r.NoError((&n).UnmarshalText([]byte("bates")))
 	r.Equal("bates", n.String())
 }
+
+func Benchmark_New(b *testing.B) {
+
+	table := []string{
+		"",
+		"widget",
+		"widget_id",
+		"WidgetID",
+		"Widget_ID",
+		"widget_ID",
+		"widget/ID",
+		"widgetID",
+		"widgetName",
+		"JWTName",
+		"JWTname",
+		"jwtname",
+		"sql",
+		"sQl",
+		"id",
+		"Id",
+		"iD",
+		"html",
+		"Html",
+		"HTML",
+		"with `code` inside",
+		"Donald E. Knuth",
+		"Random text with *(bad)* characters",
+		"Allow_Under_Scores",
+		"Trailing bad characters!@#",
+		"!@#Leading bad characters",
+		"Squeeze	 separators",
+		"Test with + sign",
+		"Malmö",
+		"Garçons",
+		"Opsů",
+		"Ærøskøbing",
+		"Aßlar",
+		"Japanese: 日本語",
+	}
+
+	for n := 0; n < b.N; n++ {
+		for i := range table {
+			New(table[i])
+		}
+	}
+}
diff --git a/underscore.go b/underscore.go
index b92488a..e1466d9 100644
--- a/underscore.go
+++ b/underscore.go
@@ -18,16 +18,17 @@ func Underscore(s string) string {
 //	Nice to see you! = nice_to_see_you
 //	widgetID = widget_id
 func (i Ident) Underscore() Ident {
-	var out []string
+	out := make([]string, 0, len(i.Parts))
 	for _, part := range i.Parts {
-		var x string
+		var x strings.Builder
+		x.Grow(len(part))
 		for _, c := range part {
 			if unicode.IsLetter(c) || unicode.IsDigit(c) {
-				x += string(c)
+				x.WriteRune(c)
 			}
 		}
-		if x != "" {
-			out = append(out, x)
+		if x.Len() > 0 {
+			out = append(out, x.String())
 		}
 	}
 	return New(strings.ToLower(strings.Join(out, "_")))
diff --git a/underscore_test.go b/underscore_test.go
index 2425738..7122e9d 100644
--- a/underscore_test.go
+++ b/underscore_test.go
@@ -27,3 +27,22 @@ func Test_Underscore(t *testing.T) {
 		})
 	}
 }
+
+func Benchmark_Underscore(b *testing.B) {
+
+	table := []string{
+		"",
+		"bob dylan",
+		"Nice to see you!",
+		"*hello*",
+		"i've read a book! have you?",
+		"This is `code` ok",
+		"TLCForm",
+	}
+
+	for n := 0; n < b.N; n++ {
+		for i := range table {
+			Underscore(table[i])
+		}
+	}
+}