diff --git a/CHANGELOG.md b/CHANGELOG.md
index d56c0a355f..58860259a8 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -69,6 +69,7 @@ Ref: https://keepachangelog.com/en/1.0.0/
 * (query) [87d3a43](https://github.com/cosmos/cosmos-sdk/commit/87d3a432af95f4cf96aa02351ed5fcc51cca6e7b) Fix collection filtered pagination.
 * (sims) [#23952](https://github.com/cosmos/cosmos-sdk/pull/23952) Use liveness matrix for validator sign status in sims
 * (baseapp) [#24055](https://github.com/cosmos/cosmos-sdk/pull/24055) Align block header when query with latest height.
+* (baseapp) [#24074](https://github.com/cosmos/cosmos-sdk/pull/24074) Use CometBFT's ComputeProtoSizeForTxs in defaultTxSelector.SelectTxForProposal for consistency.
 
 ## [v0.50.12](https://github.com/cosmos/cosmos-sdk/releases/tag/v0.50.12) - 2025-02-20
 
diff --git a/baseapp/abci_utils.go b/baseapp/abci_utils.go
index 649ad4230b..51b7b94e56 100644
--- a/baseapp/abci_utils.go
+++ b/baseapp/abci_utils.go
@@ -11,6 +11,7 @@ import (
 	cryptoenc "github.com/cometbft/cometbft/crypto/encoding"
 	cmtprotocrypto "github.com/cometbft/cometbft/proto/tendermint/crypto"
 	cmtproto "github.com/cometbft/cometbft/proto/tendermint/types"
+	cmttypes "github.com/cometbft/cometbft/types"
 	protoio "github.com/cosmos/gogoproto/io"
 	"github.com/cosmos/gogoproto/proto" //nolint: gci // ignore this line for this linter
 
@@ -497,7 +498,7 @@ func (ts *defaultTxSelector) Clear() {
 }
 
 func (ts *defaultTxSelector) SelectTxForProposal(_ context.Context, maxTxBytes, maxBlockGas uint64, memTx sdk.Tx, txBz []byte) bool {
-	txSize := uint64(len(txBz))
+	txSize := uint64(cmttypes.ComputeProtoSizeForTxs([]cmttypes.Tx{txBz}))
 
 	var txGasLimit uint64
 	if memTx != nil {
diff --git a/baseapp/abci_utils_test.go b/baseapp/abci_utils_test.go
index 42e843c2e2..d7593e3bcc 100644
--- a/baseapp/abci_utils_test.go
+++ b/baseapp/abci_utils_test.go
@@ -493,6 +493,9 @@ func (s *ABCIUtilsTestSuite) TestDefaultProposalHandler_NoOpMempoolTxSelection()
 	s.Require().NoError(err)
 	s.Require().Len(txBz, 152)
 
+	txDataSize := int(cmttypes.ComputeProtoSizeForTxs([]cmttypes.Tx{txBz}))
+	s.Require().Equal(txDataSize, 155)
+
 	testCases := map[string]struct {
 		ctx         sdk.Context
 		req         *abci.RequestPrepareProposal
@@ -514,7 +517,7 @@ func (s *ABCIUtilsTestSuite) TestDefaultProposalHandler_NoOpMempoolTxSelection()
 			}),
 			req: &abci.RequestPrepareProposal{
 				Txs:        [][]byte{txBz, txBz, txBz, txBz, txBz},
-				MaxTxBytes: 456,
+				MaxTxBytes: 465,
 			},
 			expectedTxs: 0,
 		},
@@ -522,10 +525,18 @@ func (s *ABCIUtilsTestSuite) TestDefaultProposalHandler_NoOpMempoolTxSelection()
 			ctx: s.ctx,
 			req: &abci.RequestPrepareProposal{
 				Txs:        [][]byte{txBz, txBz, txBz, txBz, txBz},
-				MaxTxBytes: 456,
+				MaxTxBytes: 465,
 			},
 			expectedTxs: 3,
 		},
+		"large max tx bytes len calculation": {
+			ctx: s.ctx,
+			req: &abci.RequestPrepareProposal{
+				Txs:        [][]byte{txBz, txBz, txBz, txBz, txBz},
+				MaxTxBytes: 456,
+			},
+			expectedTxs: 2,
+		},
 		"max gas and tx bytes": {
 			ctx: s.ctx.WithConsensusParams(cmtproto.ConsensusParams{
 				Block: &cmtproto.BlockParams{
@@ -534,7 +545,7 @@ func (s *ABCIUtilsTestSuite) TestDefaultProposalHandler_NoOpMempoolTxSelection()
 			}),
 			req: &abci.RequestPrepareProposal{
 				Txs:        [][]byte{txBz, txBz, txBz, txBz, txBz},
-				MaxTxBytes: 456,
+				MaxTxBytes: 465,
 			},
 			expectedTxs: 2,
 		},
@@ -543,7 +554,7 @@ func (s *ABCIUtilsTestSuite) TestDefaultProposalHandler_NoOpMempoolTxSelection()
 	for name, tc := range testCases {
 		s.Run(name, func() {
 			// iterate multiple times to ensure the tx selector is cleared each time
-			for i := 0; i < 5; i++ {
+			for i := 0; i < 6; i++ {
 				resp, err := handler(tc.ctx, tc.req)
 				s.Require().NoError(err)
 				s.Require().Len(resp.Txs, tc.expectedTxs)