diff --git a/pkgs/development/python-modules/calmsize/default.nix b/pkgs/development/python-modules/calmsize/default.nix
new file mode 100644
index 000000000000..10a55e2e2ff1
--- /dev/null
+++ b/pkgs/development/python-modules/calmsize/default.nix
@@ -0,0 +1,34 @@
+{
+  lib,
+  buildPythonPackage,
+  fetchFromGitHub,
+  pytestCheckHook,
+  setuptools,
+}:
+
+buildPythonPackage rec {
+  pname = "calmsize";
+  version = "0.1.3";
+  pyproject = true;
+
+  src = fetchFromGitHub {
+    owner = "Stonesjtu";
+    repo = "calmsize";
+    tag = version;
+    hash = "sha256-D4UMzgYq++w6+Od0t9mDP4S+3Tc/ME5++NOlozXXALQ=";
+  };
+
+  build-system = [ setuptools ];
+
+  nativeCheckInputs = [ pytestCheckHook ];
+
+  pythonImportsCheck = [ "calmsize" ];
+
+  meta = {
+    description = "Take a number of bytes and return a human-readable string";
+    homepage = "https://github.com/Stonesjtu/calmsize";
+    changelog = "https://github.com/Stonesjtu/calmsize/blob/${version}/CHANGES.md";
+    license = lib.licenses.zpl21;
+    maintainers = with lib.maintainers; [ jherland ];
+  };
+}
diff --git a/pkgs/top-level/python-packages.nix b/pkgs/top-level/python-packages.nix
index 5d3262b216a4..5f4d3895fc5a 100644
--- a/pkgs/top-level/python-packages.nix
+++ b/pkgs/top-level/python-packages.nix
@@ -2233,6 +2233,8 @@ self: super: with self; {
 
   calmjs-types = callPackage ../development/python-modules/calmjs-types { };
 
+  calmsize = callPackage ../development/python-modules/calmsize { };
+
   calver = callPackage ../development/python-modules/calver { };
 
   calysto = callPackage ../development/python-modules/calysto { };