diff --git a/lib/bash/parse_options.sh b/lib/bash/parse_options.sh
index 3689f82d..a33e68f8 100644
--- a/lib/bash/parse_options.sh
+++ b/lib/bash/parse_options.sh
@@ -236,6 +236,7 @@ _eval_po() {
       local opt=""
       local default_val=""
       local neg=0
+      local size=0
       while read key val; do
          case "$key" in
             long)
@@ -247,6 +248,7 @@ _eval_po() {
             "short form")
                ;;
             type)
+               [ "$val" = "size" ] && size=1
                ;;
             desc)
                ;;
@@ -273,6 +275,11 @@ _eval_po() {
          fi
       fi
 
+      # Convert sizes.
+      if [ $size -eq 1 -a -n "$default_val" ]; then
+         default_val=$(size_to_bytes $default_val)
+      fi
+
       # Eval the option into existence as a global variable.
       eval "OPT_${opt}"="$default_val"
    done
@@ -339,6 +346,7 @@ _parse_command_line() {
    local opt_is_negated=""
    local real_opt=""
    local required_arg=""
+   local spec=""
 
    for opt in "$@"; do
       if [ "$opt" = "--" -o "$opt" = "----" ]; then
@@ -438,6 +446,11 @@ _parse_command_line() {
          # Get and transform the opt's long form.  E.g.: -q == --quiet == QUIET.
          opt=$(cat "$spec" | grep '^long:' | cut -d':' -f2 | sed 's/-/_/g' | tr [:lower:] [:upper:])
 
+         # Convert sizes.
+         if grep "^type:size" "$spec" >/dev/null; then
+            val=$(size_to_bytes $val)
+         fi
+
          # Re-eval the option to update its global variable value.
          eval "OPT_$opt"="'$val'"
 
@@ -448,10 +461,16 @@ _parse_command_line() {
          opt_is_negated=""
          real_opt=""
          required_arg=""
+         spec=""
       fi
    done
 }
 
+size_to_bytes() {
+   local size="$1"
+   echo $size | perl -ne '%f=(B=>1, K=>1_024, M=>1_048_576, G=>1_073_741_824, T=>1_099_511_627_776); m/^(\d+)([kMGT])?/i; print $1 * $f{uc($2 || "B")};'
+}
+
 # ###########################################################################
 # End parse_options package
 # ###########################################################################
diff --git a/t/lib/bash/parse_options.sh b/t/lib/bash/parse_options.sh
index 9c124858..b66f8584 100644
--- a/t/lib/bash/parse_options.sh
+++ b/t/lib/bash/parse_options.sh
@@ -1,6 +1,6 @@
 #!/usr/bin/env bash
 
-TESTS=64
+TESTS=72
 
 TMPFILE="$TEST_TMPDIR/parse-opts-output"
 TOOL="pt-stalk"
@@ -183,6 +183,34 @@ is "$OPT_STRING_OPT" "hello world" "Option value with space (cmd line)"
 is "$ARGV" "" "ARGV (cmd line)"
 is "$EXT_ARGV" "" "External ARGV (cmd line)"
 
+# ############################################################################
+# Size options.
+# ############################################################################
+
+parse_options "$T_LIB_DIR/samples/bash/po004.sh" --disk-bytes-free 1T
+is "$OPT_DISK_BYTES_FREE" "1099511627776" "Size: 1T"
+
+parse_options "$T_LIB_DIR/samples/bash/po004.sh" --disk-bytes-free 1G
+is "$OPT_DISK_BYTES_FREE" "1073741824" "Size: 1G"
+
+parse_options "$T_LIB_DIR/samples/bash/po004.sh" --disk-bytes-free 1M
+is "$OPT_DISK_BYTES_FREE" "1048576" "Size: 1M"
+
+parse_options "$T_LIB_DIR/samples/bash/po004.sh" --disk-bytes-free 1K
+is "$OPT_DISK_BYTES_FREE" "1024" "Size: 1K"
+
+parse_options "$T_LIB_DIR/samples/bash/po004.sh" --disk-bytes-free 1k
+is "$OPT_DISK_BYTES_FREE" "1024" "Size: 1k"
+
+parse_options "$T_LIB_DIR/samples/bash/po004.sh" --disk-bytes-free 1
+is "$OPT_DISK_BYTES_FREE" "1" "Size: 1"
+
+parse_options "$T_LIB_DIR/samples/bash/po004.sh" --disk-bytes-free 100M
+is "$OPT_DISK_BYTES_FREE" "104857600" "Size: 100M"
+
+parse_options "$T_LIB_DIR/samples/bash/po004.sh"
+is "$OPT_DISK_BYTES_FREE" "104857600" "Size: 100M default"
+
 # ############################################################################
 # Done
 # ############################################################################
diff --git a/t/lib/samples/bash/po004.sh b/t/lib/samples/bash/po004.sh
new file mode 100644
index 00000000..0574f221
--- /dev/null
+++ b/t/lib/samples/bash/po004.sh
@@ -0,0 +1,37 @@
+#!/usr/bin/env bash
+
+:
+
+# ############################################################################
+# Documentation
+# ############################################################################
+:<<'DOCUMENTATION'
+=pod
+
+=head1 NAME
+
+pt-stalk - Wait for a condition to occur then begin collecting data.
+
+=head1 OPTIONS
+
+=over
+
+=item --disk-bytes-free
+
+type: size; default: 100M
+
+Fall apart if there's less than this many bytes free on the disk.
+
+=item --help
+
+Print help.
+
+=back
+
+=head1 ENVIRONMENT
+
+No env vars used.
+
+=cut
+
+DOCUMENTATION