diff --git a/CMakeLists.txt b/CMakeLists.txt
index d1e3d44..03d49a5 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -24,6 +24,9 @@ set(SOURCES
   src/ctype/charprops.c
   src/ctype/classes.c
   src/ctype/convert.c
+  # inttypes
+  src/inttypes/functions.c
+  src/inttypes/sizes.c
   # stdlib
   src/stdlib/arith.c
   # string
diff --git a/include/ft/all-tests.h b/include/ft/all-tests.h
index 05a210e..d43191e 100644
--- a/include/ft/all-tests.h
+++ b/include/ft/all-tests.h
@@ -13,6 +13,10 @@ extern ft_test ft_ctype_functions;
 extern ft_test ft_ctype_convert_macros;
 extern ft_test ft_ctype_convert_functions;
 
+/* inttypes */
+extern ft_test ft_inttypes_sizes;
+extern ft_test ft_inttypes_functions;
+
 /* stdlib */
 extern ft_test ft_stdlib_arith;
 
diff --git a/src/inttypes/functions.c b/src/inttypes/functions.c
new file mode 100644
index 0000000..49e7610
--- /dev/null
+++ b/src/inttypes/functions.c
@@ -0,0 +1,41 @@
+#include <inttypes.h>
+#include <limits.h>
+#include <ft/test.h>
+#include <ft/all-tests.h>
+
+static void _ft_inttypes_functions(ft_test *t)
+{
+	ft_log(t, "abs with function:\n");
+	ft_assert_eval(t, imaxabs(73ll), 73ll, "%" PRIdMAX);
+	ft_assert_eval(t, imaxabs(-73ll), 73ll, "%" PRIdMAX);
+	ft_assert_eval(t, imaxabs(0ll), 0ll, "%" PRIdMAX);
+	ft_assert_eval(t, imaxabs(LLONG_MAX), LLONG_MAX, "%" PRIdMAX);
+	/* Very edgy corner case */
+	ft_assert_eval(t, imaxabs(LLONG_MIN), LLONG_MIN, "%" PRIdMAX);
+
+	#undef imaxabs
+
+	ft_log(t, "\nabs with macro:\n");
+	ft_assert_eval(t, imaxabs(73ll), 73ll, "%" PRIdMAX);
+	ft_assert_eval(t, imaxabs(-73ll), 73ll, "%" PRIdMAX);
+	ft_assert_eval(t, imaxabs(0ll), 0ll, "%" PRIdMAX);
+	ft_assert_eval(t, imaxabs(LLONG_MAX), LLONG_MAX, "%" PRIdMAX);
+	/* Very edgy corner case */
+	ft_assert_eval(t, imaxabs(LLONG_MIN), LLONG_MIN, "%" PRIdMAX);
+
+	ft_log(t, "\ndiv: by asserts (not shown)\n");
+	imaxdiv_t imd;
+	imd = imaxdiv(73ll, 8ll);
+	ft_assert(t, imd.quot == 9ll && imd.rem == 1ll);
+	imd = imaxdiv(-73ll, 8ll);
+	ft_assert(t, imd.quot == -9ll && imd.rem == -1ll);
+	imd = imaxdiv(73ll, -8ll);
+	ft_assert(t, imd.quot == -9ll && imd.rem == 1ll);
+	imd = imaxdiv(-73ll, -8ll);
+	ft_assert(t, imd.quot == 9ll && imd.rem == -1ll);
+}
+
+ft_test ft_inttypes_functions = {
+	.name = "Extended integer functions",
+	.function = _ft_inttypes_functions,
+};
diff --git a/src/inttypes/sizes.c b/src/inttypes/sizes.c
new file mode 100644
index 0000000..20ad43c
--- /dev/null
+++ b/src/inttypes/sizes.c
@@ -0,0 +1,49 @@
+#include <inttypes.h>
+#include <stddef.h>
+#include <ft/test.h>
+#include <ft/all-tests.h>
+
+static void _inttypes_sizes(ft_test *t)
+{
+	ft_assert(t, sizeof(int8_t) == sizeof(uint8_t));
+	ft_assert(t, sizeof(int16_t) == sizeof(uint16_t));
+	ft_assert(t, sizeof(int32_t) == sizeof(uint32_t));
+	ft_assert(t, sizeof(int64_t) == sizeof(uint64_t));
+	ft_assert(t, sizeof(int_least8_t) == sizeof(uint_least8_t));
+	ft_assert(t, sizeof(int_least16_t) == sizeof(uint_least16_t));
+	ft_assert(t, sizeof(int_least32_t) == sizeof(uint_least32_t));
+	ft_assert(t, sizeof(int_least64_t) == sizeof(uint_least64_t));
+	ft_assert(t, sizeof(int_fast8_t) == sizeof(uint_fast8_t));
+	ft_assert(t, sizeof(int_fast16_t) == sizeof(uint_fast16_t));
+	ft_assert(t, sizeof(int_fast32_t) == sizeof(uint_fast32_t));
+	ft_assert(t, sizeof(int_fast64_t) == sizeof(uint_fast64_t));
+	ft_assert(t, sizeof(intmax_t) == sizeof(uintmax_t));
+	ft_assert(t, sizeof(intptr_t) == sizeof(uintptr_t));
+
+	/* TODO: Use %zu once available in *printf */
+	ft_log(t, "Size of integer types:\n\n");
+
+	ft_log(t, " %d  int8_t\n", (int)sizeof(uint8_t));
+	ft_log(t, " %d  int16_t\n", (int)sizeof(uint16_t));
+	ft_log(t, " %d  int32_t\n", (int)sizeof(uint32_t));
+	ft_log(t, " %d  int64_t\n\n", (int)sizeof(uint64_t));
+
+	ft_log(t, " %d  int_least8_t\n", (int)sizeof(uint_least8_t));
+	ft_log(t, " %d  int_least16_t\n", (int)sizeof(uint_least16_t));
+	ft_log(t, " %d  int_least32_t\n", (int)sizeof(uint_least32_t));
+	ft_log(t, " %d  int_least64_t\n\n", (int)sizeof(uint_least64_t));
+
+	ft_log(t, " %d  int_fast8_t\n", (int)sizeof(uint_fast8_t));
+	ft_log(t, " %d  int_fast16_t\n", (int)sizeof(uint_fast16_t));
+	ft_log(t, " %d  int_fast32_t\n", (int)sizeof(uint_fast32_t));
+	ft_log(t, " %d  int_fast64_t\n\n", (int)sizeof(uint_fast64_t));
+
+	ft_log(t, " %d  intmax_t\n", (int)sizeof(uintmax_t));
+	ft_log(t, " %d  intptr_t\n", (int)sizeof(uintptr_t));
+	ft_log(t, " %d  size_t\n", (int)sizeof(size_t));
+}
+
+ft_test ft_inttypes_sizes = {
+	.name = "Size of integer types",
+	.function = _inttypes_sizes,
+};
diff --git a/src/main.c b/src/main.c
index 5e1a990..af2cea1 100644
--- a/src/main.c
+++ b/src/main.c
@@ -20,6 +20,11 @@ ft_list headers_libc[] = {
         &ft_ctype_convert_functions,
         NULL,
     }},
+    { "<inttypes.h>", (ft_test*[]){
+        &ft_inttypes_sizes,
+        &ft_inttypes_functions,
+        NULL,
+    }},
     { "<locale.h>", NULL },
     { "<setjmp.h>", NULL },
     { "<signal.h>", NULL },