diff --git a/mdbx.h b/mdbx.h
index f7c9ff59..21aa371b 100644
--- a/mdbx.h
+++ b/mdbx.h
@@ -918,8 +918,7 @@ LIBMDBX_API int mdbx_env_set_maxdbs(MDBX_env *env, MDBX_dbi dbs);
  * [in] env  An environment handle returned by mdbx_env_create()
  *
  * Returns The maximum size of a key we can write. */
-LIBMDBX_API int mdbx_env_get_maxkeysize(MDBX_env *env);
-LIBMDBX_API int mdbx_get_maxkeysize(size_t pagesize);
+LIBMDBX_API intptr_t mdbx_env_get_maxkeysize(MDBX_env *env);
 
 /* Set application information associated with the MDBX_env.
  *
@@ -1692,6 +1691,13 @@ LIBMDBX_API int mdbx_is_dirty(const MDBX_txn *txn, const void *ptr);
 LIBMDBX_API int mdbx_dbi_sequence(MDBX_txn *txn, MDBX_dbi dbi, uint64_t *result,
                                   uint64_t increment);
 
+LIBMDBX_API intptr_t mdbx_limits_pgsize_min(void);
+LIBMDBX_API intptr_t mdbx_limits_pgsize_max(void);
+LIBMDBX_API intptr_t mdbx_limits_dbsize_min(intptr_t pagesize);
+LIBMDBX_API intptr_t mdbx_limits_dbsize_max(intptr_t pagesize);
+LIBMDBX_API intptr_t mdbx_limits_keysize_max(intptr_t pagesize);
+LIBMDBX_API intptr_t mdbx_limits_txnsize_max(intptr_t pagesize);
+
 /*----------------------------------------------------------------------------*/
 /* attribute support functions for Nexenta */
 typedef uint_fast64_t mdbx_attr_t;
diff --git a/src/mdbx.c b/src/mdbx.c
index ab41be88..812475b0 100644
--- a/src/mdbx.c
+++ b/src/mdbx.c
@@ -4921,7 +4921,7 @@ fail:
   return rc;
 }
 
-int __cold mdbx_env_get_maxkeysize(MDBX_env *env) {
+intptr_t __cold mdbx_env_get_maxkeysize(MDBX_env *env) {
   if (!env || env->me_signature != MDBX_ME_SIGNATURE || !env->me_maxkey_limit)
     return -MDBX_EINVAL;
   return env->me_maxkey_limit;
@@ -4935,18 +4935,6 @@ int __cold mdbx_env_get_maxkeysize(MDBX_env *env) {
 #define mdbx_maxgc_ov1page(pagesize)                                           \
   (((pagesize)-PAGEHDRSZ) / sizeof(pgno_t) - 1)
 
-int mdbx_get_maxkeysize(size_t pagesize) {
-  if (pagesize == 0)
-    pagesize = mdbx_syspagesize();
-
-  intptr_t nodemax = mdbx_nodemax(pagesize);
-  if (nodemax < 0)
-    return -MDBX_EINVAL;
-
-  intptr_t maxkey = mdbx_maxkey(nodemax);
-  return (maxkey > 0 && maxkey < INT_MAX) ? (int)maxkey : -MDBX_EINVAL;
-}
-
 static void __cold mdbx_setup_pagesize(MDBX_env *env, const size_t pagesize) {
   STATIC_ASSERT(SSIZE_MAX > MAX_MAPSIZE);
   STATIC_ASSERT(MIN_PAGESIZE > sizeof(MDBX_page));
@@ -12325,6 +12313,53 @@ int mdbx_dbi_sequence(MDBX_txn *txn, MDBX_dbi dbi, uint64_t *result,
   return MDBX_SUCCESS;
 }
 
+/*----------------------------------------------------------------------------*/
+
+__cold intptr_t mdbx_limits_keysize_max(intptr_t pagesize) {
+  if (pagesize < 1)
+    pagesize = (intptr_t)mdbx_syspagesize();
+  else if (unlikely(pagesize < MIN_PAGESIZE || pagesize > MAX_PAGESIZE ||
+                    !mdbx_is_power2((size_t)pagesize)))
+    return -MDBX_EINVAL;
+
+  return mdbx_maxkey(mdbx_nodemax(pagesize));
+}
+
+__cold intptr_t mdbx_limits_pgsize_min(void) { return MIN_PAGESIZE; }
+
+__cold intptr_t mdbx_limits_pgsize_max(void) { return MAX_PAGESIZE; }
+
+__cold intptr_t mdbx_limits_dbsize_min(intptr_t pagesize) {
+  if (pagesize < 1)
+    pagesize = (intptr_t)mdbx_syspagesize();
+  else if (unlikely(pagesize < MIN_PAGESIZE || pagesize > MAX_PAGESIZE ||
+                    !mdbx_is_power2((size_t)pagesize)))
+    return -MDBX_EINVAL;
+
+  return MIN_PAGENO * pagesize;
+}
+
+__cold intptr_t mdbx_limits_dbsize_max(intptr_t pagesize) {
+  if (pagesize < 1)
+    pagesize = (intptr_t)mdbx_syspagesize();
+  else if (unlikely(pagesize < MIN_PAGESIZE || pagesize > MAX_PAGESIZE ||
+                    !mdbx_is_power2((size_t)pagesize)))
+    return -MDBX_EINVAL;
+
+  const intptr_t limit = MAX_PAGENO * pagesize;
+  return ((size_t)limit < MAX_MAPSIZE) ? limit : MAX_PAGESIZE;
+}
+
+__cold intptr_t mdbx_limits_txnsize_max(intptr_t pagesize) {
+  if (pagesize < 1)
+    pagesize = (intptr_t)mdbx_syspagesize();
+  else if (unlikely(pagesize < MIN_PAGESIZE || pagesize > MAX_PAGESIZE ||
+                    !mdbx_is_power2((size_t)pagesize)))
+    return -MDBX_EINVAL;
+
+  return pagesize * (MDBX_LIST_MAX - 1);
+}
+
 /*----------------------------------------------------------------------------*/
 /* attribute support functions for Nexenta */
 
diff --git a/test/main.cc b/test/main.cc
index e6e0e177..17b3d718 100644
--- a/test/main.cc
+++ b/test/main.cc
@@ -1,4 +1,4 @@
-/*
+/*
  * Copyright 2017-2018 Leonid Yuriev <leo@yuriev.ru>
  * and other libmdbx authors: please see AUTHORS file.
  * All rights reserved.
@@ -193,10 +193,10 @@ int main(int argc, char *const argv[]) {
         params.keylen_max = params.keylen_min;
       continue;
     }
-    if (config::parse_option(
-            argc, argv, narg, "keylen.max", params.keylen_max, config::no_scale,
-            0, std::min(mdbx_get_maxkeysize(0), (int)UINT16_MAX))) {
-
+    if (config::parse_option(argc, argv, narg, "keylen.max", params.keylen_max,
+                             config::no_scale, 0,
+                             std::min((unsigned)mdbx_limits_keysize_max(0),
+                                      (unsigned)UINT16_MAX))) {
       if (params.keylen_min > params.keylen_max)
         params.keylen_min = params.keylen_max;
       continue;