diff --git a/day1/day1.py b/day1/day1.py
new file mode 100644
index 0000000..55009a3
--- /dev/null
+++ b/day1/day1.py
@@ -0,0 +1,41 @@
+#! /usr/bin/env python3
+
+
+def calculate_fuel_iterative(mass):
+    total = 0
+    new_mass = mass
+    while True:
+        new_mass = new_mass // 3 - 2
+        if new_mass < 0:
+            break
+        total += new_mass
+    return total
+
+
+def calculate_total_fuel_mass(input_file, mass_function=lambda x: x // 3 - 2):
+    total = 0
+    with open(input_file) as masses:
+        for mass in masses:
+            total += mass_function(int(mass))
+    return total
+
+
+def test_part2():
+    inputs = (14, 1969, 100756)
+    expected = (2, 966, 50346)
+    for i, inp in enumerate(inputs):
+        result = calculate_fuel_iterative(inp)
+        assert result == expected[i], "Result for {} should be {}, was {}".format(
+            inp, expected[i], result
+        )
+    print("All tests passed for part 2.")
+
+
+if __name__ == "__main__":
+    print("Part 1 - total mass: ", calculate_total_fuel_mass("./input.txt"))
+
+    test_part2()
+    print(
+        "Part 2 -- total mass: ",
+        calculate_total_fuel_mass("./input.txt", calculate_fuel_iterative),
+    )
diff --git a/day1/input.txt b/day1/input.txt
new file mode 100644
index 0000000..ab07505
--- /dev/null
+++ b/day1/input.txt
@@ -0,0 +1,100 @@
+62259
+75368
+93740
+119724
+112546
+137714
+96999
+130673
+102398
+73819
+100734
+85337
+62764
+82115
+127696
+54391
+103213
+77954
+112513
+112392
+138404
+92989
+108521
+83163
+109720
+91918
+114443
+54306
+90623
+66833
+58505
+85919
+77539
+149419
+128385
+66452
+94677
+109179
+62072
+137245
+136226
+145783
+60689
+103320
+145931
+101286
+63458
+122468
+87858
+105675
+146185
+57417
+96883
+70739
+97494
+140951
+149416
+83137
+66122
+134319
+58511
+139600
+102929
+112240
+149634
+64142
+83332
+129526
+99058
+148889
+50087
+74961
+133606
+143518
+68849
+97045
+73920
+61357
+115941
+56740
+111773
+77880
+90792
+77103
+111355
+125898
+56547
+84918
+113822
+74113
+98557
+80928
+60519
+146379
+59354
+102490
+72584
+59000
+63151
+114253