diff --git a/electrum/fee_policy.py b/electrum/fee_policy.py
index 33b7eb384..f02e545c8 100644
--- a/electrum/fee_policy.py
+++ b/electrum/fee_policy.py
@@ -2,6 +2,7 @@ from typing import Optional, Sequence, Tuple, Union, TYPE_CHECKING, Dict
 from decimal import Decimal
 from numbers import Real
 from enum import IntEnum
+import math
 
 from .i18n import _
 from .util import NoDynamicFeeEstimates, quantize_feerate, format_fee_satoshis
@@ -257,11 +258,15 @@ class FeePolicy(Logger):
             else:
                 raise NoDynamicFeeEstimates()
 
-        return self.estimate_fee_for_feerate(fee_per_kb, size)
+        return self.estimate_fee_for_feerate(fee_per_kb=fee_per_kb, size=size)
 
     @classmethod
-    def estimate_fee_for_feerate(cls, fee_per_kb: Union[int, float, Decimal],
-                                 size: Union[int, float, Decimal]) -> int:
+    def estimate_fee_for_feerate(
+        cls,
+        *,
+        fee_per_kb: Union[int, float, Decimal],
+        size: Union[int, float, Decimal],
+    ) -> int:
         # note: 'size' is in vbytes
         size = Decimal(size)
         fee_per_kb = Decimal(fee_per_kb)
@@ -269,7 +274,7 @@ class FeePolicy(Logger):
         # to be consistent with what is displayed in the GUI,
         # the calculation needs to use the same precision:
         fee_per_byte = quantize_feerate(fee_per_byte)
-        return round(fee_per_byte * size)
+        return math.ceil(fee_per_byte * size)
 
 
 class FixedFeePolicy(FeePolicy):
diff --git a/electrum/gui/qml/qetxfinalizer.py b/electrum/gui/qml/qetxfinalizer.py
index 1b378d608..5e691732a 100644
--- a/electrum/gui/qml/qetxfinalizer.py
+++ b/electrum/gui/qml/qetxfinalizer.py
@@ -887,8 +887,8 @@ class QETxCpfpFeeBumper(TxFeeSlider, TxMonMixin):
     def get_child_fee_from_total_feerate(self, fee_per_kb: Optional[int]) -> Optional[int]:
         if fee_per_kb is None:
             return None
-        fee = fee_per_kb * self._total_size / 1000 - self._parent_fee
-        fee = round(fee)
+        package_fee = FeePolicy.estimate_fee_for_feerate(fee_per_kb=fee_per_kb, size=self._total_size)
+        fee = package_fee - self._parent_fee
         fee = min(self._max_fee, fee)
         fee = max(self._total_size, fee)  # pay at least 1 sat/byte for combined size
         return fee
diff --git a/electrum/gui/qt/confirm_tx_dialog.py b/electrum/gui/qt/confirm_tx_dialog.py
index 6ab873331..d6047eb24 100644
--- a/electrum/gui/qt/confirm_tx_dialog.py
+++ b/electrum/gui/qt/confirm_tx_dialog.py
@@ -350,7 +350,10 @@ class TxEditor(WindowModalDialog):
                 # fallback to actual fee
                 displayed_feerate = quantize_feerate(fee / size) if fee is not None else None
                 self.feerate_e.setAmount(displayed_feerate)
-            displayed_fee = round(displayed_feerate * size) if displayed_feerate is not None else None
+            if displayed_feerate is not None:
+                displayed_fee = FeePolicy.estimate_fee_for_feerate(fee_per_kb=displayed_feerate * 1000, size=size)
+            else:
+                displayed_fee = None
             self.fee_e.setAmount(displayed_fee)
         else:
             if freeze_fee:
diff --git a/electrum/gui/qt/main_window.py b/electrum/gui/qt/main_window.py
index ef69b7208..21c5c286e 100644
--- a/electrum/gui/qt/main_window.py
+++ b/electrum/gui/qt/main_window.py
@@ -2874,8 +2874,8 @@ class ElectrumWindow(QMainWindow, MessageBoxMixin, Logger, QtEventListener):
         def get_child_fee_from_total_feerate(fee_per_kb: Optional[int]) -> Optional[int]:
             if fee_per_kb is None:
                 return None
-            fee = fee_per_kb * total_size / 1000 - parent_fee
-            fee = round(fee)
+            package_fee = FeePolicy.estimate_fee_for_feerate(fee_per_kb=fee_per_kb, size=total_size)
+            fee = package_fee - parent_fee
             fee = min(max_fee, fee)
             fee = max(total_size, fee)  # pay at least 1 sat/byte for combined size
             return fee