diff --git a/h_malloc.c b/h_malloc.c
index f03a74e..aed2078 100644
--- a/h_malloc.c
+++ b/h_malloc.c
@@ -194,7 +194,7 @@ static inline struct size_info get_size_info(size_t size) {
         return (struct size_info){0, 0};
     }
     if (size <= 128) {
-        return (struct size_info){(size + 15) & ~15, ((size - 1) >> 4) + 1};
+        return (struct size_info){align(size, 16), ((size - 1) >> 4) + 1};
     }
     for (unsigned class = 9; class < N_SIZE_CLASSES; class++) {
         size_t real_size = size_classes[class];
@@ -217,7 +217,7 @@ static inline struct size_info get_size_info_align(size_t size, size_t alignment
 }
 
 static size_t get_slab_size(size_t slots, size_t size) {
-    return PAGE_CEILING(slots * size);
+    return page_align(slots * size);
 }
 
 struct __attribute__((aligned(CACHELINE_SIZE))) size_class {
@@ -1202,9 +1202,9 @@ static size_t get_large_size_class(size_t size) {
         size = max(size, (size_t)PAGE_SIZE);
         size_t spacing_shift = 64 - __builtin_clzl(size - 1) - 3;
         size_t spacing_class = 1ULL << spacing_shift;
-        return (size + (spacing_class - 1)) & ~(spacing_class - 1);
+        return align(size, spacing_class);
     }
-    return PAGE_CEILING(size);
+    return page_align(size);
 }
 
 static size_t get_guard_size(struct random_state *state, size_t size) {
@@ -1480,7 +1480,7 @@ EXPORT void *h_realloc(void *old, size_t size) {
                     deallocate_pages(old, old_size, old_guard_size);
                 } else {
                     memory_unmap((char *)old - old_guard_size, old_guard_size);
-                    memory_unmap((char *)old + PAGE_CEILING(old_size), old_guard_size);
+                    memory_unmap((char *)old + page_align(old_size), old_guard_size);
                 }
                 thread_seal_metadata();
                 return new;
@@ -1524,7 +1524,7 @@ EXPORT void *h_valloc(size_t size) {
 }
 
 EXPORT void *h_pvalloc(size_t size) {
-    size = PAGE_CEILING(size);
+    size = page_align(size);
     if (unlikely(!size)) {
         errno = ENOMEM;
         return NULL;
diff --git a/pages.c b/pages.c
index 505c884..27558de 100644
--- a/pages.c
+++ b/pages.c
@@ -9,10 +9,6 @@ static bool add_guards(size_t size, size_t guard_size, size_t *total_size) {
         __builtin_add_overflow(*total_size, guard_size, total_size);
 }
 
-static uintptr_t alignment_ceiling(uintptr_t s, uintptr_t alignment) {
-    return ((s) + (alignment - 1)) & ((~alignment) + 1);
-}
-
 void *allocate_pages(size_t usable_size, size_t guard_size, bool unprotect, const char *name) {
     size_t real_size;
     if (unlikely(add_guards(usable_size, guard_size, &real_size))) {
@@ -33,7 +29,7 @@ void *allocate_pages(size_t usable_size, size_t guard_size, bool unprotect, cons
 }
 
 void *allocate_pages_aligned(size_t usable_size, size_t alignment, size_t guard_size, const char *name) {
-    usable_size = PAGE_CEILING(usable_size);
+    usable_size = page_align(usable_size);
     if (unlikely(!usable_size)) {
         errno = ENOMEM;
         return NULL;
@@ -59,7 +55,7 @@ void *allocate_pages_aligned(size_t usable_size, size_t alignment, size_t guard_
 
     void *usable = (char *)real + guard_size;
 
-    size_t lead_size = alignment_ceiling((uintptr_t)usable, alignment) - (uintptr_t)usable;
+    size_t lead_size = align((uintptr_t)usable, alignment) - (uintptr_t)usable;
     size_t trail_size = alloc_size - lead_size - usable_size;
     void *base = (char *)usable + lead_size;
 
diff --git a/pages.h b/pages.h
index f0943cb..2874b48 100644
--- a/pages.h
+++ b/pages.h
@@ -5,11 +5,16 @@
 #include <stddef.h>
 #include <stdint.h>
 
+#include "util.h"
+
 #define PAGE_SHIFT 12
 #ifndef PAGE_SIZE
 #define PAGE_SIZE ((size_t)1 << PAGE_SHIFT)
 #endif
-#define PAGE_CEILING(s) (((s) + PAGE_SIZE - 1) & ~(PAGE_SIZE - 1))
+
+static inline size_t page_align(size_t size) {
+    return align(size, PAGE_SIZE);
+}
 
 void *allocate_pages(size_t usable_size, size_t guard_size, bool unprotect, const char *name);
 void *allocate_pages_aligned(size_t usable_size, size_t alignment, size_t guard_size, const char *name);
diff --git a/util.h b/util.h
index 4c7ac9f..6df2563 100644
--- a/util.h
+++ b/util.h
@@ -1,6 +1,7 @@
 #ifndef UTIL_H
 #define UTIL_H
 
+#include <stddef.h>
 #include <stdint.h>
 
 // C11 noreturn doesn't work in C++
@@ -32,6 +33,11 @@ static inline int ffzl(unsigned long x) {
     return __builtin_ffsl(~x);
 }
 
+static inline size_t align(size_t size, size_t align) {
+    size_t mask = align - 1;
+    return (size + mask) & ~mask;
+}
+
 COLD noreturn void fatal_error(const char *s);
 
 typedef uint8_t u8;