diff --git a/lib/day1/day1.ex b/lib/day1/day1.ex
new file mode 100644
index 0000000..2718f0f
--- /dev/null
+++ b/lib/day1/day1.ex
@@ -0,0 +1,35 @@
+defmodule Day1 do
+  def part1 do
+    File.read!("lib/day1/input.txt")
+    |> String.split("\n")
+    |> Enum.reject(&(&1 == ""))
+    |> Enum.map(fn line ->
+      {module, _} = Integer.parse(line)
+      fuel_for(module)
+    end)
+    |> Enum.sum()
+  end
+
+  def part2 do
+    File.read!("lib/day1/input.txt")
+    |> String.split("\n")
+    |> Enum.reject(&(&1 == ""))
+    |> Enum.map(fn line ->
+      {module, _} = Integer.parse(line)
+      total_fuel(module)
+    end)
+    |> Enum.sum()
+  end
+
+  def total_fuel(mass \\ part1())
+  def total_fuel(mass) when mass <= 0, do: mass
+
+  def total_fuel(mass) do
+    fuel_mass = fuel_for(mass)
+    fuel_mass + total_fuel(fuel_mass)
+  end
+
+  def fuel_for(mass) do
+    max(Integer.floor_div(mass, 3) - 2, 0)
+  end
+end
diff --git a/lib/day1/input.txt b/lib/day1/input.txt
new file mode 100644
index 0000000..e2e824d
--- /dev/null
+++ b/lib/day1/input.txt
@@ -0,0 +1,100 @@
+89122
+141123
+91549
+66506
+53504
+56517
+77050
+92298
+84853
+141828
+86739
+126125
+82793
+113761
+68961
+132576
+61718
+64498
+110415
+134867
+102449
+107364
+88491
+120584
+52192
+130494
+121583
+132166
+111339
+68715
+104966
+117227
+58921
+83909
+70626
+141637
+95127
+72029
+136121
+136915
+74312
+54863
+53547
+149493
+78528
+132289
+148754
+133905
+135357
+58483
+62214
+124684
+118590
+107087
+95768
+86835
+122277
+126183
+108546
+75212
+62280
+76039
+135743
+86133
+111613
+139477
+65930
+106225
+101531
+96501
+66844
+114158
+137091
+138143
+102083
+69857
+59372
+137605
+108135
+96365
+94851
+104414
+74194
+74188
+131888
+75910
+78279
+93285
+53597
+82705
+119360
+149274
+92510
+95490
+54087
+97695
+94753
+80493
+101173
+51906
\ No newline at end of file