diff --git a/tools/free_space.awk b/tools/free_space.awk
deleted file mode 100755
index 1f2b04415..000000000
--- a/tools/free_space.awk
+++ /dev/null
@@ -1,13 +0,0 @@
-#!/usr/bin/awk -f
-
-# Usage: tools/free_space.awk pokecrystal.map
-
-BEGIN {
-	total = free = 16384 * 128
-}
-/^  SECTION: \$[0-7]/ {
-	free -= strtonum("0x" substr($3, 3))
-}
-END {
-	printf "Free space: %d/%d (%.2f%%)\n", free, total, free * 100 / total
-}
diff --git a/tools/free_space.py b/tools/free_space.py
new file mode 100644
index 000000000..4df8aec9d
--- /dev/null
+++ b/tools/free_space.py
@@ -0,0 +1,73 @@
+#!/usr/bin/env python3
+# -*- coding: utf-8 -*-
+
+"""
+Usage: python3 free_space.py [BANK=none] [pokecrystal.map]
+
+Calculate the free space in the ROM or its individual banks.
+
+The BANK argument allows printing free space in one, all, or none of the ROM's banks.
+Valid arguments are numbers (in decimal "42" or hexadecimal "0x2A"), "all" or "none".
+If not specified, defaults to "none".
+"""
+
+import sys
+
+from mapreader import MapReader
+
+def main():
+	print_bank = 'none'
+	mapfile = 'pokecrystal.map'
+
+	if len(sys.argv) >= 2 and sys.argv[1].startswith('BANK='):
+		print_bank = sys.argv[1].split('=', 1)[-1]
+		if len(sys.argv) >= 3:
+			mapfile = sys.argv[2]
+	elif len(sys.argv) >= 3 and sys.argv[2].startswith('BANK='):
+		print_bank = sys.argv[2].split('=', 1)[-1]
+		mapfile = sys.argv[1]
+
+	if print_bank not in {'all', 'none'}:
+		try:
+			if print_bank.startswith('0x') or print_bank.startswith('0X'):
+				print_bank = int(print_bank[2:], 16)
+			else:
+				print_bank = int(print_bank)
+		except ValueError:
+			error = 'Error: invalid BANK: %s' % print_bank
+			if print_bank.isalnum():
+				error += ' (did you mean: 0x%s?)' % print_bank
+			print(error, file=sys.stderr)
+			sys.exit(1)
+
+	num_banks = 0x80
+	bank_size = 0x4000 # bytes
+	total_size = num_banks * bank_size
+
+	r = MapReader()
+	with open(mapfile, 'r', encoding='utf-8') as f:
+		l = f.readlines()
+	r.read_map_data(l)
+
+	free_space = 0
+	per_bank = []
+	default_bank_data = {'sections': [], 'used': 0, 'slack': bank_size}
+	for bank in range(num_banks):
+		bank_data = r.bank_data['ROM0 bank'] if bank == 0 else r.bank_data['ROMX bank']
+		data = bank_data.get(bank, default_bank_data)
+		used = data['used']
+		slack = data['slack']
+		per_bank.append((used, slack))
+		free_space += slack
+
+	print('Free space: %d/%d (%.2f%%)' % (free_space, total_size, free_space * 100.0 / total_size))
+	if print_bank != 'none':
+		print()
+		print('bank, used, free')
+	for bank in range(num_banks):
+		used, slack = per_bank[bank]
+		if print_bank in {'all', bank}:
+				print('$%02X, %d, %d' % (bank, used, slack))
+
+if __name__ == '__main__':
+	main()