diff --git a/doc/release-notes.md b/doc/release-notes.md
--- a/doc/release-notes.md
+++ b/doc/release-notes.md
@@ -8,3 +8,7 @@
  - Improve SHA256 performance using SSE4.1, AVX2 and/or SHA if available.
  - Add a mode argument to the `getmemoryinfo` RPC call to query `malloc_info` from the system if available.
  - Disable safe mode by default
+ - Update fee calculation to add 1790 effective bytes per transaction output in excess of inputs.
+   Refund 1790 bytes worth of minimum fee per input in excess of outputs to a minimum of
+   10 + 34 * (number of utxos)
+ - Drop min relay fee to 100sat/kb
diff --git a/src/policy/policy.h b/src/policy/policy.h
--- a/src/policy/policy.h
+++ b/src/policy/policy.h
@@ -29,7 +29,7 @@
  * Default for -blockmintxfee, which sets the minimum feerate for a transaction
  * in blocks created by mining code.
  */
-static const Amount DEFAULT_BLOCK_MIN_TX_FEE_PER_KB(1000 * SATOSHI);
+static const Amount DEFAULT_BLOCK_MIN_TX_FEE_PER_KB(100 * SATOSHI);
 /**
  * The maximum size for transactions we're willing to relay/mine.
  */
diff --git a/src/primitives/transaction.cpp b/src/primitives/transaction.cpp
--- a/src/primitives/transaction.cpp
+++ b/src/primitives/transaction.cpp
@@ -115,7 +115,22 @@
 }
 
 size_t CTransaction::GetBillableSize() const {
-    return ::GetSerializeSize(*this, SER_NETWORK, PROTOCOL_VERSION);
+
+    size_t nTxSize = GetTotalSize(), inputs = vin.size(), outputs = vout.size();
+
+    // 179 bytes is the minimum size it would take to spend any outputs which
+    // are created.  We want to change in advance of spending them to
+    // incentivize keeping your UTXO set reasonbly sized.
+    int64_t modSize =
+        int64_t(nTxSize) + (int64_t(outputs) - int64_t(inputs)) * 1790;
+
+    // Note: It is impossible to generate a negative number above in any real
+    // world situation.  This is because the inputs have a least 179 byte
+    // each. However, it is possible to have shorter scriptSigs than 179
+    // bytes.  Therefore, we include a minimum of 10 bytes + 34 * vouts.
+    nTxSize = std::max(int64_t(outputs * 34 + 10), modSize);
+
+    return nTxSize;
 }
 
 unsigned int CTransaction::GetTotalSize() const {
diff --git a/src/test/transaction_tests.cpp b/src/test/transaction_tests.cpp
--- a/src/test/transaction_tests.cpp
+++ b/src/test/transaction_tests.cpp
@@ -800,7 +800,7 @@
             auto txSize = tx.GetTotalSize();
             BOOST_CHECK(txBillableSize > 0);
             if (inputs > outputs) {
-                BOOST_CHECK(txBillableSize <= txSize);
+                BOOST_CHECK(txBillableSize < txSize);
             } else {
                 BOOST_CHECK(txBillableSize >= txSize);
             }
diff --git a/src/txmempool.cpp b/src/txmempool.cpp
--- a/src/txmempool.cpp
+++ b/src/txmempool.cpp
@@ -782,17 +782,20 @@
                                   nNoLimit, nNoLimit, dummy);
         uint64_t nCountCheck = setAncestors.size() + 1;
         uint64_t nSizeCheck = it->GetTxSize();
+        uint64_t nBillableSizeCheck = it->GetTxBillableSize();
         Amount nFeesCheck = it->GetModifiedFee();
         int64_t nSigOpCheck = it->GetSigOpCount();
 
         for (txiter ancestorIt : setAncestors) {
             nSizeCheck += ancestorIt->GetTxSize();
+            nBillableSizeCheck += ancestorIt->GetTxBillableSize();
             nFeesCheck += ancestorIt->GetModifiedFee();
             nSigOpCheck += ancestorIt->GetSigOpCount();
         }
 
         assert(it->GetCountWithAncestors() == nCountCheck);
         assert(it->GetSizeWithAncestors() == nSizeCheck);
+        assert(it->GetBillableSizeWithAncestors() == nBillableSizeCheck);
         assert(it->GetSigOpCountWithAncestors() == nSigOpCheck);
         assert(it->GetModFeesWithAncestors() == nFeesCheck);
 
diff --git a/src/validation.h b/src/validation.h
--- a/src/validation.h
+++ b/src/validation.h
@@ -59,7 +59,7 @@
 /** Default for DEFAULT_WHITELISTFORCERELAY. */
 static const bool DEFAULT_WHITELISTFORCERELAY = true;
 /** Default for -minrelaytxfee, minimum relay fee for transactions */
-static const Amount DEFAULT_MIN_RELAY_TX_FEE_PER_KB(1000 * SATOSHI);
+static const Amount DEFAULT_MIN_RELAY_TX_FEE_PER_KB(100 * SATOSHI);
 /** Default for -excessutxocharge for transactions transactions */
 static const Amount DEFAULT_UTXO_FEE = Amount::zero();
 //! -maxtxfee default
diff --git a/test/functional/fundrawtransaction.py b/test/functional/fundrawtransaction.py
--- a/test/functional/fundrawtransaction.py
+++ b/test/functional/fundrawtransaction.py
@@ -152,7 +152,7 @@
 
         inputs = [{'txid': utx['txid'], 'vout': utx['vout']}]
         outputs = {
-            self.nodes[0].getnewaddress(): Decimal(5.0) - fee - feeTolerance}
+            self.nodes[0].getnewaddress(): satoshi_round(Decimal(5.0) - fee - feeTolerance)}
         rawtx = self.nodes[2].createrawtransaction(inputs, outputs)
         dec_tx = self.nodes[2].decoderawtransaction(rawtx)
         assert_equal(utx['txid'], dec_tx['vin'][0]['txid'])
diff --git a/test/functional/test_framework/mininode.py b/test/functional/test_framework/mininode.py
--- a/test/functional/test_framework/mininode.py
+++ b/test/functional/test_framework/mininode.py
@@ -406,7 +406,17 @@
         """
         Returns the size used for billing the against the transaction
         """
-        return len(self.serialize())
+        # We need a heuristic for unsigned transactions as they do not yet
+        # include the pubkey hash, or the signature.
+        tx_size = 10  # base transaction overhead
+        for vin in self.vin:
+            # Max of sig + p2kh, or the actual size if it's more.
+            tx_size += max(len(ToHex(vin))//2, 147)
+        for vout in self.vout:
+            # Include the sizes for the outputs.
+            tx_size += len(ToHex(vout))//2
+        tx_size += (len(self.vout) - len(self.vin))*1790
+        return max(tx_size, 10 + 34 * len(self.vout))
 
     def serialize(self):
         r = b""