diff --git a/converter-main/main.go b/converter-main/main.go
index 1535238..5d7b47b 100644
--- a/converter-main/main.go
+++ b/converter-main/main.go
@@ -12,5 +12,9 @@ func main() {
 	input := os.Args[1]
 	convTo := os.Args[2]
 
-	fmt.Println(converter.Convert(input, convTo))
+	result, err := converter.Convert(input, convTo)
+	if err != nil {
+		log.Fatalln(err)
+	}
+	fmt.Println(result)
 }
diff --git a/converter/converter.go b/converter/converter.go
index dc51f27..9654236 100644
--- a/converter/converter.go
+++ b/converter/converter.go
@@ -1,7 +1,7 @@
 package converter
 
+import "errors"
 import "fmt"
-import "log"
 import "strconv"
 import "strings"
 
@@ -22,7 +22,7 @@ var (
 	convVal float64
 )
 
-func Convert(input, convTo string) string {
+func Convert(input, convTo string) (string, error) {
 	switch {
 	case strings.HasSuffix(input, markerKm):
 		inUnit = markerKm
@@ -33,11 +33,11 @@ func Convert(input, convTo string) string {
 	case strings.HasSuffix(input, markerMiles):
 		inUnit = markerMiles
 	default:
-		log.Fatalln("Invalid input:", input)
+		return "", errors.New("Invalid input: " + input)
 	}
 	inVal, err = strconv.ParseFloat(input[:len(input)-len(inUnit)], 64)
 	if err != nil {
-		log.Fatalln("Invalid input number", err)
+		return "", errors.New("Invalid input number (" + err.Error() + ")")
 	}
 
 	switch inUnit {
@@ -61,8 +61,8 @@ func Convert(input, convTo string) string {
 	case markerMeter:
 		convVal = asMeter
 	default:
-		log.Fatalln("Invalid unit: " + convTo)
+		return "", errors.New("Invalid unit: " + convTo)
 	}
 
-	return fmt.Sprintf("%.2f%s", convVal, convTo)
+	return fmt.Sprintf("%.2f%s", convVal, convTo), nil
 }