diff --git a/src/qt/modaloverlay.cpp b/src/qt/modaloverlay.cpp
index d3d389ed280..28848fa03af 100644
--- a/src/qt/modaloverlay.cpp
+++ b/src/qt/modaloverlay.cpp
@@ -163,12 +163,14 @@ void ModalOverlay::tipUpdate(int count, const QDateTime& blockDate, double nVeri
 
 void ModalOverlay::UpdateHeaderSyncLabel() {
     int est_headers_left = bestHeaderDate.secsTo(QDateTime::currentDateTime()) / Params().GetConsensus().nPowTargetSpacing;
-    ui->numberOfBlocksLeft->setText(tr("Unknown. Syncing Headers (%1, %2%)…").arg(bestHeaderHeight).arg(QString::number(100.0 / (bestHeaderHeight + est_headers_left) * bestHeaderHeight, 'f', 1)));
+    const int pct = bestHeaderHeight ? static_cast<int>(1000LL * bestHeaderHeight / (bestHeaderHeight + est_headers_left)) : 0;
+    ui->numberOfBlocksLeft->setText(tr("Unknown. Syncing Headers (%1, %2%)…").arg(bestHeaderHeight).arg(QStringLiteral("%1.%2").arg(pct / 10).arg(pct % 10)));
 }
 
 void ModalOverlay::UpdateHeaderPresyncLabel(int height, const QDateTime& blockDate) {
     int est_headers_left = blockDate.secsTo(QDateTime::currentDateTime()) / Params().GetConsensus().nPowTargetSpacing;
-    ui->numberOfBlocksLeft->setText(tr("Unknown. Pre-syncing Headers (%1, %2%)…").arg(height).arg(QString::number(100.0 / (height + est_headers_left) * height, 'f', 1)));
+    const int pct = height ? static_cast<int>(1000LL * height / (height + est_headers_left)) : 0;
+    ui->numberOfBlocksLeft->setText(tr("Unknown. Pre-syncing Headers (%1, %2%)…").arg(height).arg(QStringLiteral("%1.%2").arg(pct / 10).arg(pct % 10)));
 }
 
 void ModalOverlay::toggleVisibility()