diff --git a/usr/lib/archboot/iso.sh b/usr/lib/archboot/iso.sh
index 185efacb4..997d86837 100644
--- a/usr/lib/archboot/iso.sh
+++ b/usr/lib/archboot/iso.sh
@@ -213,7 +213,7 @@ _prepare_extlinux_image() {
     echo "Prepare extlinux image ..."
     ## get size of boot files
     BOOTSIZE=$(du -bc "${_ISODIR}"/boot | grep total | cut -f1)
-    IMGSZ=$(((BOOTSIZE)/1024 + 21000)) # image size in sectors
+    IMGSZ=$(((BOOTSIZE*117)/100/1024)) # image size in sectors
     ## Create extlinux.img
     dd if=/dev/zero of="${_ISODIR}"/extlinux.img bs="${IMGSZ}" count=1024 status=none
     EXT_IMAGE="${_ISODIR}/extlinux.img"