diff --git a/src/mainwindow.cpp b/src/mainwindow.cpp
index 1da35f2..0e7da86 100644
--- a/src/mainwindow.cpp
+++ b/src/mainwindow.cpp
@@ -148,17 +148,12 @@ MainWindow::MainWindow(QWidget *parent)
   ui->tableWidget->setFocus();
   setAcceptDrops(true);
 
-  // Build the list of known factors (all combinations).
+  // Build the list of known factors.
   ui->knownFactors->addItem("", 100.0);
-  for (int i = 0; i < FACTORS_LABELS.size(); i++) {
-    for (int j = 0; j < FACTORS_LABELS.size(); j++) {
-      if (i == j) {
-        continue;
-      }
-      ui->knownFactors->addItem(
-          QString("%1 → %2").arg(FACTORS_LABELS[i]).arg(FACTORS_LABELS[j]),
-          FACTORS_VALUES[j] / FACTORS_VALUES[i] * 100.0);
-    }
+  foreach (Factor conv, FACTORS_VALUES) {
+    ui->knownFactors->addItem(
+        QString("%1 fps → %2 fps").arg(conv.first).arg(conv.second),
+        conv.first * 100.0 / conv.second);
   }
 
   // Disable print out by default.
@@ -1130,14 +1125,16 @@ void MainWindow::actionShowHelp() {
 }
 
 void MainWindow::speedFactorChanged(double p_factor) {
-  if (FACTORS_VALUES.indexOf(p_factor) >= 0) {
+  if (qAbs(p_factor - ui->knownFactors->currentData().toDouble()) > 0.001) {
     ui->knownFactors->setCurrentIndex(-1);
   }
 }
 
-void MainWindow::knownFactorChosen(int) {
+void MainWindow::knownFactorChosen(int p_chosen) {
   // Adjust spinbox to known factor.
-  ui->speedFactor->setValue(ui->knownFactors->currentData().toDouble());
+  if (p_chosen >= 0) {
+    ui->speedFactor->setValue(ui->knownFactors->itemData(p_chosen).toDouble());
+  }
 }
 
 void MainWindow::enableKnownFactors(bool p_state) {
diff --git a/src/mainwindow.h b/src/mainwindow.h
index 8647b8b..05461c3 100644
--- a/src/mainwindow.h
+++ b/src/mainwindow.h
@@ -23,6 +23,7 @@
 #include <QMainWindow>
 #include <QMap>
 #include <QModelIndex>
+#include <QPair>
 #include <QString>
 #include <QTableWidget>
 #include <QTime>
@@ -38,9 +39,11 @@
 
 #define MAX_RECENT_FILES 7
 
-static QList<double> FACTORS_VALUES = {23.976, 24, 25, 29.97, 30};
-static QStringList FACTORS_LABELS = {"23,976 fps", "24 fps", "25 fps",
-                                     "29,97 fps", "30 fps"};
+typedef QPair<double, double> Factor;
+static QList<Factor> FACTORS_VALUES = {
+    {23.976, 24}, {23.976, 25}, {24, 23.976}, {24, 25},
+    {25, 23.976}, {25, 24},     {29.97, 30},  {30, 29.97},
+};
 
 class ConfigEditor;
 class ShortcutEditor;