diff --git a/src/mainwindow.cpp b/src/mainwindow.cpp
--- a/src/mainwindow.cpp
+++ b/src/mainwindow.cpp
@@ -59,6 +59,9 @@ const QMap<int, QString> panelSettingMap
         {6, "Log"}
     });
 
+const char* BPS_TOOLTIP = "bits per second";
+const char* BPS_TOOLTIP_ERR = "Maximum baud rate may be reached!";
+
 MainWindow::MainWindow(QWidget *parent) :
     QMainWindow(parent),
     ui(new Ui::MainWindow),
@@ -233,7 +236,7 @@ MainWindow::MainWindow(QWidget *parent) 
 
     // init bps (bits per second) counter
     bpsLabel.setText("0bps");
-    bpsLabel.setToolTip(tr("bits per second"));
+    bpsLabel.setToolTip(tr(BPS_TOOLTIP));
     ui->statusBar->addPermanentWidget(&bpsLabel);
     connect(&bpsTimer, &QTimer::timeout,
             this, &MainWindow::onBpsTimeout);
@@ -372,6 +375,7 @@ void MainWindow::onPortToggled(bool open
         bpsTimer.stop();
         // if not cleared last displayed value is stuck
         bpsLabel.setText("0bps");
+        bpsLabel.setToolTip(tr(BPS_TOOLTIP));
         spsLabel.setText("0sps");
     }
 }
@@ -404,7 +408,20 @@ void MainWindow::onSpsChanged(float sps)
 void MainWindow::onBpsTimeout()
 {
     unsigned bits = dataFormatPanel.getBytesRead() * 8;
-    bpsLabel.setText(QString("%1bps").arg(bits));
+    unsigned maxBps = portControl.maxBitRate();
+    QString str;
+    if (bits >= maxBps)
+    {
+        // TODO: an icon for bps warning
+        str = QString(tr("!%1/%2bps")).arg(bits).arg(maxBps);
+        bpsLabel.setToolTip(tr(BPS_TOOLTIP_ERR));
+    }
+    else
+    {
+        str = QString(tr("%1bps")).arg(bits);
+        bpsLabel.setToolTip(tr(BPS_TOOLTIP));
+    }
+    bpsLabel.setText(str);
 }
 
 bool MainWindow::isDemoRunning()
diff --git a/src/portcontrol.cpp b/src/portcontrol.cpp
--- a/src/portcontrol.cpp
+++ b/src/portcontrol.cpp
@@ -1,5 +1,5 @@
 /*
-  Copyright © 2017 Hasan Yavuz Özderya
+  Copyright © 2019 Hasan Yavuz Özderya
 
   This file is part of serialplot.
 
@@ -453,6 +453,27 @@ QString PortControl::currentFlowControlT
     }
 }
 
+unsigned PortControl::maxBitRate() const
+{
+    float baud = serialPort->baudRate();
+    float dataBits = serialPort->dataBits();
+    float parityBits = serialPort->parity() == QSerialPort::NoParity ? 0 : 1;
+
+    float stopBits;
+    if (serialPort->stopBits() == QSerialPort::OneAndHalfStop)
+    {
+        stopBits = 1.5;
+    }
+    else
+    {
+        stopBits = serialPort->stopBits();
+    }
+
+    float frame_size = 1 /* start bit */ + dataBits + parityBits + stopBits;
+
+    return float(baud) / frame_size;
+}
+
 void PortControl::saveSettings(QSettings* settings)
 {
     settings->beginGroup(SettingGroup_Port);
diff --git a/src/portcontrol.h b/src/portcontrol.h
--- a/src/portcontrol.h
+++ b/src/portcontrol.h
@@ -1,5 +1,5 @@
 /*
-  Copyright © 2017 Hasan Yavuz Özderya
+  Copyright © 2019 Hasan Yavuz Özderya
 
   This file is part of serialplot.
 
@@ -47,6 +47,9 @@ public:
     QSerialPort* serialPort;
     QToolBar* toolBar();
 
+    /// Returns maximum bit rate for current baud rate
+    unsigned maxBitRate() const;
+
     /// Stores port settings into a `QSettings`
     void saveSettings(QSettings* settings);
     /// Loads port settings from a `QSettings`. If open serial port is closed.