diff --git a/src/init.cpp b/src/init.cpp
--- a/src/init.cpp
+++ b/src/init.cpp
@@ -401,7 +401,7 @@
                                       DEFAULT_MAX_ORPHAN_TRANSACTIONS));
     strUsage += HelpMessageOpt("-maxmempool=<n>",
                                strprintf(_("Keep the transaction memory pool "
-                                           "below <n> megabytes (default: %u)"),
+                                           "below <n> bytes (default: %u)"),
                                          DEFAULT_MAX_MEMPOOL_SIZE));
     strUsage +=
         HelpMessageOpt("-mempoolexpiry=<n>",
@@ -1539,7 +1539,7 @@
 
     // mempool limits
     int64_t nMempoolSizeMax =
-        gArgs.GetArg("-maxmempool", DEFAULT_MAX_MEMPOOL_SIZE) * 1000000;
+        gArgs.GetArg("-maxmempool", DEFAULT_MAX_MEMPOOL_SIZE);
     int64_t nMempoolSizeMin =
         gArgs.GetArg("-limitdescendantsize", DEFAULT_DESCENDANT_SIZE_LIMIT) *
         1000 * 40;
@@ -2024,7 +2024,7 @@
     // the rest goes to in-memory cache
     nCoinCacheUsage = nTotalCache;
     int64_t nMempoolSizeMax =
-        gArgs.GetArg("-maxmempool", DEFAULT_MAX_MEMPOOL_SIZE) * 1000000;
+        gArgs.GetArg("-maxmempool", DEFAULT_MAX_MEMPOOL_SIZE);
     LogPrintf("Cache configuration:\n");
     LogPrintf("* Using %.1fMiB for block index database\n",
               nBlockTreeDBCache * (1.0 / 1024 / 1024));
diff --git a/src/policy/policy.h b/src/policy/policy.h
--- a/src/policy/policy.h
+++ b/src/policy/policy.h
@@ -54,9 +54,9 @@
  */
 static const unsigned int MAX_STANDARD_TX_SIGOPS = MAX_TX_SIGOPS_COUNT / 5;
 /**
- * Default for -maxmempool, maximum megabytes of mempool memory usage.
+ * Default for -maxmempool, maximum bytes of mempool memory usage.
  */
-static const unsigned int DEFAULT_MAX_MEMPOOL_SIZE = 300;
+static const unsigned int DEFAULT_MAX_MEMPOOL_SIZE = 300000000;
 /**
  * Default for -incrementalrelayfee, which sets the minimum feerate increase for
  * mempool limiting or BIP 125 replacement.
diff --git a/src/rpc/blockchain.cpp b/src/rpc/blockchain.cpp
--- a/src/rpc/blockchain.cpp
+++ b/src/rpc/blockchain.cpp
@@ -1442,8 +1442,7 @@
     ret.pushKV("size", (int64_t)g_mempool.size());
     ret.pushKV("bytes", (int64_t)g_mempool.GetTotalTxSize());
     ret.pushKV("usage", (int64_t)g_mempool.DynamicMemoryUsage());
-    size_t maxmempool =
-        gArgs.GetArg("-maxmempool", DEFAULT_MAX_MEMPOOL_SIZE) * 1000000;
+    size_t maxmempool = gArgs.GetArg("-maxmempool", DEFAULT_MAX_MEMPOOL_SIZE);
     ret.pushKV("maxmempool", (int64_t)maxmempool);
     ret.pushKV("mempoolminfee",
                ValueFromAmount(g_mempool.GetMinFee(maxmempool).GetFeePerK()));
diff --git a/src/txmempool.cpp b/src/txmempool.cpp
--- a/src/txmempool.cpp
+++ b/src/txmempool.cpp
@@ -954,7 +954,7 @@
     LOCK(cs);
 
     uint64_t maxMempoolSize =
-        gArgs.GetArg("-maxmempool", DEFAULT_MAX_MEMPOOL_SIZE) * 1000000;
+        gArgs.GetArg("-maxmempool", DEFAULT_MAX_MEMPOOL_SIZE);
     // minerPolicy uses recent blocks to figure out a reasonable fee.  This
     // may disagree with the rollingMinimumFeerate under certain scenarios
     // where the mempool  increases rapidly, or blocks are being mined which
@@ -1389,7 +1389,7 @@
                              STANDARD_LOCKTIME_VERIFY_FLAGS);
 
     // Re-limit mempool size, in case we added any transactions
-    g_mempool.LimitSize(
-        gArgs.GetArg("-maxmempool", DEFAULT_MAX_MEMPOOL_SIZE) * 1000000,
-        gArgs.GetArg("-mempoolexpiry", DEFAULT_MEMPOOL_EXPIRY) * 60 * 60);
+    g_mempool.LimitSize(gArgs.GetArg("-maxmempool", DEFAULT_MAX_MEMPOOL_SIZE),
+                        gArgs.GetArg("-mempoolexpiry", DEFAULT_MEMPOOL_EXPIRY) *
+                            60 * 60);
 }
diff --git a/src/validation.cpp b/src/validation.cpp
--- a/src/validation.cpp
+++ b/src/validation.cpp
@@ -554,8 +554,7 @@
         CFeeRate minRelayTxFee = config.GetMinFeePerKB();
         Amount mempoolRejectFee =
             pool.GetMinFee(
-                    gArgs.GetArg("-maxmempool", DEFAULT_MAX_MEMPOOL_SIZE) *
-                    1000000)
+                    gArgs.GetArg("-maxmempool", DEFAULT_MAX_MEMPOOL_SIZE))
                 .GetFee(nSize);
         if (mempoolRejectFee > Amount::zero() &&
             nModifiedFees < mempoolRejectFee) {
@@ -725,7 +724,7 @@
         // Trim mempool and check if tx was trimmed.
         if (!fOverrideMempoolLimit) {
             pool.LimitSize(
-                gArgs.GetArg("-maxmempool", DEFAULT_MAX_MEMPOOL_SIZE) * 1000000,
+                gArgs.GetArg("-maxmempool", DEFAULT_MAX_MEMPOOL_SIZE),
                 gArgs.GetArg("-mempoolexpiry", DEFAULT_MEMPOOL_EXPIRY) * 60 *
                     60);
             if (!pool.exists(txid)) {
@@ -2004,7 +2003,7 @@
                 nLastSetChain = nNow;
             }
             int64_t nMempoolSizeMax =
-                gArgs.GetArg("-maxmempool", DEFAULT_MAX_MEMPOOL_SIZE) * 1000000;
+                gArgs.GetArg("-maxmempool", DEFAULT_MAX_MEMPOOL_SIZE);
             int64_t cacheSize = pcoinsTip->DynamicMemoryUsage();
             int64_t nTotalSpace =
                 nCoinCacheUsage +