diff --git a/decor/counters.go b/decor/counters.go
index f4c9764..4d58164 100644
--- a/decor/counters.go
+++ b/decor/counters.go
@@ -45,6 +45,9 @@
 		wc = widthConf
 	}
 	wc.Init()
+	if pairFmt == "" {
+		pairFmt = "%d / %d"
+	}
 	d := &countersDecorator{
 		WC:      wc,
 		unit:    unit,
diff --git a/decor/percentage.go b/decor/percentage.go
index 38bacf3..c9f88e0 100644
--- a/decor/percentage.go
+++ b/decor/percentage.go
@@ -25,25 +25,29 @@
 		}
 	}
 
-	res := strconv.FormatFloat(float64(s), 'f', prec, 64)
+	var b strings.Builder
+	b.WriteString(strconv.FormatFloat(float64(s), 'f', prec, 64))
 
 	if st.Flag(' ') {
-		res += " "
+		b.WriteString(" ")
 	}
-	res += "%"
+	b.WriteString("%")
 
 	if w, ok := st.Width(); ok {
-		if len(res) < w {
-			pad := strings.Repeat(" ", w-len(res))
+		if l := b.Len(); l < w {
+			pad := strings.Repeat(" ", w-l)
 			if st.Flag('-') {
-				res += pad
+				b.WriteString(pad)
 			} else {
-				res = pad + res
+				tmp := b.String()
+				b.Reset()
+				b.WriteString(pad)
+				b.WriteString(tmp)
 			}
 		}
 	}
 
-	io.WriteString(st, res)
+	io.WriteString(st, b.String())
 }
 
 // Percentage returns percentage decorator. It's a wrapper of NewPercentage.
@@ -66,6 +70,9 @@
 		wc = widthConf
 	}
 	wc.Init()
+	if fmt == "" {
+		fmt = "% d"
+	}
 	d := &percentageDecorator{
 		WC:  wc,
 		fmt: fmt,
diff --git a/decor/speed.go b/decor/speed.go
index 679c683..e90b0ff 100644
--- a/decor/speed.go
+++ b/decor/speed.go
@@ -40,8 +40,10 @@
 		wc = widthConf
 	}
 	wc.Init()
-	switch unit {
-	case UnitKiB, UnitKB:
+	if fmt == "" {
+		fmt = "%.0f"
+	}
+	if unit > 0 {
 		fmt += "/s"
 	}
 	d := &movingAverageSpeed{
@@ -130,8 +132,10 @@
 		wc = widthConf
 	}
 	wc.Init()
-	switch unit {
-	case UnitKiB, UnitKB:
+	if fmt == "" {
+		fmt = "%.0f"
+	}
+	if unit > 0 {
 		fmt += "/s"
 	}
 	d := &averageSpeed{
diff --git a/decor/speed_test.go b/decor/speed_test.go
index 1f8a69f..4f16aea 100644
--- a/decor/speed_test.go
+++ b/decor/speed_test.go
@@ -15,6 +15,14 @@
 		expected string
 	}{
 		{
+			name:     "empty fmt",
+			unit:     UnitKiB,
+			fmt:      "",
+			current:  0,
+			elapsed:  time.Second,
+			expected: "0b/s",
+		},
+		{
 			name:     "UnitKiB:%d:0b",
 			unit:     UnitKiB,
 			fmt:      "%d",
@@ -135,6 +143,14 @@
 		expected string
 	}{
 		{
+			name:     "empty fmt",
+			unit:     UnitKB,
+			fmt:      "",
+			current:  0,
+			elapsed:  time.Second,
+			expected: "0b/s",
+		},
+		{
 			name:     "UnitKB:%d:0b",
 			unit:     UnitKB,
 			fmt:      "%d",