diff --git a/main.go b/main.go
index 529cf85..6428348 100644
--- a/main.go
+++ b/main.go
@@ -3,6 +3,7 @@ package main
 import (
 	"encoding/csv"
 	"encoding/json"
+	"flag"
 	"fmt"
 	"log"
 	"net/http"
@@ -91,6 +92,9 @@ func TradesHandler(w http.ResponseWriter, r *http.Request) {
 // ---------- Main ----------
 
 func main() {
+	port := flag.String("port", "8081", "port to listen on")
+	flag.Parse()
+
 	http.HandleFunc("/styles.css", Styles)
 	http.HandleFunc("/", Home)
 	http.HandleFunc("/about", About)
@@ -102,8 +106,8 @@ func main() {
 	http.HandleFunc("/trades", TradesHandler)
 	http.HandleFunc("/api/prices", PricesHandler)
 
-	fmt.Println("running on http://localhost:8081/")
-	if err := http.ListenAndServe(":8081", nil); err != nil {
+	fmt.Printf("running on http://localhost:%s/\n", *port)
+	if err := http.ListenAndServe(":"+*port, nil); err != nil {
 		log.Fatal(err)
 	}
 }