diff --git a/tools/mkimage-raw-bios/make-bios b/tools/mkimage-raw-bios/make-bios
index 95dbddb12..abec07d65 100755
--- a/tools/mkimage-raw-bios/make-bios
+++ b/tools/mkimage-raw-bios/make-bios
@@ -52,8 +52,7 @@ ESP_FILE_SIZE=$(( $KERNEL_FILE_SIZE + $INITRD_FILE_SIZE + $ESP_HEADROOM ))
 # we will round up to the nearest multiple of 2048 blocks
 # since each block is 512 bytes, we want the size to be a multiple of
 # 2048 blocks * 512 bytes = 1048576 bytes = 1024KB
-ESP_FILE_SIZE_KB=$(( ( ($ESP_FILE_SIZE+1024) / 1024 ) / 1024 * 1024 ))
-ESP_FILE_SIZE_MB=$(( $ESP_FILE_SIZE_KB / 1024 ))
+ESP_FILE_SIZE_KB=$(( ( ( ($ESP_FILE_SIZE+1024-1) / 1024 ) + 1024-1) / 1024 * 1024 ))
 # and for sectors
 ESP_FILE_SIZE_SECTORS=$(( $ESP_FILE_SIZE_KB * 2 ))
 
diff --git a/tools/mkimage-raw-efi/make-efi b/tools/mkimage-raw-efi/make-efi
index 3c026c4db..dc5aae33d 100755
--- a/tools/mkimage-raw-efi/make-efi
+++ b/tools/mkimage-raw-efi/make-efi
@@ -76,7 +76,7 @@ ESP_FILE_SIZE=$(( $KERNEL_FILE_SIZE + $INITRD_FILE_SIZE + $EFI_FILE_SIZE + $ESP_
 # we will round up to the nearest multiple of 2048 blocks
 # since each block is 512 bytes, we want the size to be a multiple of
 # 2048 blocks * 512 bytes = 1048576 bytes = 1024KB
-ESP_FILE_SIZE_KB=$(( ( ($ESP_FILE_SIZE+1024) / 1024 ) / 1024 * 1024 ))
+ESP_FILE_SIZE_KB=$(( ( ( ($ESP_FILE_SIZE+1024-1) / 1024 ) + 1024-1) / 1024 * 1024 ))
 # and for sectors
 ESP_FILE_SIZE_SECTORS=$(( $ESP_FILE_SIZE_KB * 2 ))