diff --git a/picard.wdl b/picard.wdl
index d778e172d99be2dc5f198f19a9e8f215c7e3a63c..8962c4b615a621000601c8ad4c374bfe2f2c814d 100644
--- a/picard.wdl
+++ b/picard.wdl
@@ -368,7 +368,8 @@ task GatherBamFiles {
         Int javaXmxMb = 1024
         Int compressionLevel = 1
         Boolean createMd5File = false
-        Int timeMinutes = 1 + ceil(size(inputBams, "G") * 0.5)
+        # One minute per input gigabyte.
+        Int timeMinutes = 1 + ceil(size(inputBams, "G") * 1)
         String dockerImage = "quay.io/biocontainers/picard:2.20.5--0"
     }