diff --git a/speedtest.go b/speedtest.go
index 23c0a7e..90c43e9 100644
--- a/speedtest.go
+++ b/speedtest.go
@@ -30,6 +30,8 @@ var (
 	noUpload     = kingpin.Flag("no-upload", "Disable upload test.").Bool()
 	pingMode     = kingpin.Flag("ping-mode", "Select a method for Ping. (support icmp/tcp/http)").Default("http").String()
 	debug        = kingpin.Flag("debug", "Enable debug mode.").Short('d').Bool()
+	dlSize       = kingpin.Flag("dl-size", "Set download chunk size.").Default("1000").Int()
+	ulSize       = kingpin.Flag("ul-size", "Set upload chunk size.").Default("800").Int()
 )
 
 func main() {
@@ -52,6 +54,8 @@ func main() {
 			Keyword:      *search,
 			NoDownload:   *noDownload,
 			NoUpload:     *noUpload,
+			DlSize:       *dlSize,
+			UlSize:       *ulSize,
 		}))
 	speedtestClient.SetNThread(*thread)
 
diff --git a/speedtest/request.go b/speedtest/request.go
index 332bb63..125b9d3 100644
--- a/speedtest/request.go
+++ b/speedtest/request.go
@@ -8,6 +8,7 @@ import (
 	"math"
 	"net/http"
 	"net/url"
+	"slices"
 	"strconv"
 	"strings"
 	"time"
@@ -98,10 +99,18 @@ func (s *Server) downloadTestContext(ctx context.Context, downloadRequest downlo
 		dbg.Println("Download test disabled")
 		return nil
 	}
+
+	dlSize := dlSizes[3]
+	if s.Context.config.DlSize > 0 && slices.Contains(dlSizes[:], s.Context.config.DlSize) {
+		dlSize = s.Context.config.DlSize
+	} else {
+		dbg.Printf("Invalid download size: %d. Using default size: %d.\n", s.Context.config.DlSize, dlSize)
+	}
+
 	start := time.Now()
 	_context, cancel := context.WithCancel(ctx)
 	s.Context.RegisterDownloadHandler(func() {
-		_ = downloadRequest(_context, s, 3)
+		_ = downloadRequest(_context, s, dlSize)
 	}).Start(cancel, 0)
 	duration := time.Since(start)
 	s.DLSpeed = s.Context.GetAvgDownloadRate()
@@ -125,10 +134,18 @@ func (s *Server) uploadTestContext(ctx context.Context, uploadRequest uploadFunc
 		dbg.Println("Upload test disabled")
 		return nil
 	}
+
+	ulSize := ulSizes[4]
+	if s.Context.config.UlSize > 0 && slices.Contains(ulSizes[:], s.Context.config.UlSize) {
+		ulSize = s.Context.config.UlSize
+	} else {
+		dbg.Printf("Invalid upload size: %d. Using default size: %d.\n", s.Context.config.UlSize, ulSize)
+	}
+
 	start := time.Now()
 	_context, cancel := context.WithCancel(ctx)
 	s.Context.RegisterUploadHandler(func() {
-		_ = uploadRequest(_context, s, 4)
+		_ = uploadRequest(_context, s, ulSize)
 	}).Start(cancel, 0)
 	duration := time.Since(start)
 	s.ULSpeed = s.Context.GetAvgUploadRate()
@@ -137,8 +154,7 @@ func (s *Server) uploadTestContext(ctx context.Context, uploadRequest uploadFunc
 	return nil
 }
 
-func downloadRequest(ctx context.Context, s *Server, w int) error {
-	size := dlSizes[w]
+func downloadRequest(ctx context.Context, s *Server, size int) error {
 	xdlURL := strings.Split(s.URL, "/upload.php")[0] + "/random" + strconv.Itoa(size) + "x" + strconv.Itoa(size) + ".jpg"
 	dbg.Printf("XdlURL: %s\n", xdlURL)
 	req, err := http.NewRequestWithContext(ctx, http.MethodGet, xdlURL, nil)
@@ -154,8 +170,7 @@ func downloadRequest(ctx context.Context, s *Server, w int) error {
 	return s.Context.NewChunk().DownloadHandler(resp.Body)
 }
 
-func uploadRequest(ctx context.Context, s *Server, w int) error {
-	size := ulSizes[w]
+func uploadRequest(ctx context.Context, s *Server, size int) error {
 	dc := s.Context.NewChunk().UploadHandler(int64(size*100-51) * 10)
 	req, err := http.NewRequestWithContext(ctx, http.MethodPost, s.URL, dc)
 	req.ContentLength = dc.(*DataChunk).ContentLength
diff --git a/speedtest/speedtest.go b/speedtest/speedtest.go
index c52250a..8c629db 100644
--- a/speedtest/speedtest.go
+++ b/speedtest/speedtest.go
@@ -52,6 +52,9 @@ type UserConfig struct {
 
 	NoDownload bool
 	NoUpload   bool
+
+	DlSize int
+	UlSize int
 }
 
 func parseAddr(addr string) (string, string) {