diff --git a/zetaclient/bitcoin_client.go b/zetaclient/bitcoin_client.go
index 72bce508cb..a0cd8b19cf 100644
--- a/zetaclient/bitcoin_client.go
+++ b/zetaclient/bitcoin_client.go
@@ -459,14 +459,14 @@ func (ob *BitcoinChainClient) PostGasPrice() error {
 	if feeResult.Errors != nil || feeResult.FeeRate == nil {
 		return fmt.Errorf("error getting gas price: %s", feeResult.Errors)
 	}
-	gasPrice := big.NewFloat(0)
-	gasPriceU64, _ := gasPrice.Mul(big.NewFloat(*feeResult.FeeRate), big.NewFloat(1e8)).Uint64()
+	feeRate := new(big.Int).SetInt64(int64(*feeResult.FeeRate * 1e8))
+	feeRatePerByte := new(big.Int).Div(feeRate, big.NewInt(1000))
 	bn, err := ob.rpcClient.GetBlockCount()
 	if err != nil {
 		return err
 	}
 	// #nosec G701 always positive
-	zetaHash, err := ob.zetaClient.PostGasPrice(ob.chain, gasPriceU64, "100", uint64(bn))
+	zetaHash, err := ob.zetaClient.PostGasPrice(ob.chain, feeRatePerByte.Uint64(), "100", uint64(bn))
 	if err != nil {
 		ob.logger.WatchGasPrice.Err(err).Msg("PostGasPrice:")
 		return err
diff --git a/zetaclient/btc_signer.go b/zetaclient/btc_signer.go
index a31f77bc85..1880089ec4 100644
--- a/zetaclient/btc_signer.go
+++ b/zetaclient/btc_signer.go
@@ -23,6 +23,8 @@ import (
 
 const (
 	maxNoOfInputsPerTx = 20
+	minFee             = 5_000 // 0.00005 BTC
+	estimateSizeKB     = 2     // 2K is a conservative estimate for a 20-input, 3-output tx
 )
 
 type BTCSigner struct {
@@ -59,9 +61,9 @@ func NewBTCSigner(cfg config.BTCConfig, tssSigner TSSSigner, logger zerolog.Logg
 }
 
 // SignWithdrawTx receives utxos sorted by value, amount in BTC, feeRate in BTC per Kb
-func (signer *BTCSigner) SignWithdrawTx(to *btcutil.AddressWitnessPubKeyHash, amount float64, gasPrice *big.Int, btcClient *BitcoinChainClient, height uint64, nonce uint64, chain *common.Chain) (*wire.MsgTx, error) {
-	estimateFee := 0.0001 // 10,000 sats, should be good for testnet
-	minFee := 0.00005
+func (signer *BTCSigner) SignWithdrawTx(to *btcutil.AddressWitnessPubKeyHash, amount float64, gasPrice *big.Int, sizeLimit uint64,
+	btcClient *BitcoinChainClient, height uint64, nonce uint64, chain *common.Chain) (*wire.MsgTx, error) {
+	estimateFee := float64(gasPrice.Uint64()) * estimateSizeKB / 1e8
 	nonceMark := NonceMarkAmount(nonce)
 
 	// refresh unspent UTXOs and continue with keysign regardless of error
@@ -93,8 +95,15 @@ func (signer *BTCSigner) SignWithdrawTx(to *btcutil.AddressWitnessPubKeyHash, am
 		return nil, err
 	}
 
+	// size checking
+	txSize := uint64(tx.SerializeSize())
+	// if txSize > sizeLimit {
+	// 	fmt.Printf("tx size %d is greater than sizeLimit %d; use sizeLimit", txSize, sizeLimit)
+	// 	txSize = sizeLimit
+	// }
+
 	// fee checking
-	fees := new(big.Int).Mul(big.NewInt(int64(tx.SerializeSize())), gasPrice)
+	fees := new(big.Int).Mul(big.NewInt(int64(txSize)), gasPrice)
 	fees.Div(fees, big.NewInt(1000)) //FIXME: feeRate KB is 1000B or 1024B?
 	// #nosec G701 always in range
 	if fees.Int64() < int64(minFee*1e8) {
@@ -102,6 +111,12 @@ func (signer *BTCSigner) SignWithdrawTx(to *btcutil.AddressWitnessPubKeyHash, am
 		// #nosec G701 always in range
 		fees = big.NewInt(int64(minFee * 1e8))
 	}
+	// #nosec G701 always in range
+	if fees.Int64() > int64(estimateFee*1e8) {
+		fmt.Printf("fees %d is greater than estimateFee %f; use estimateFee", fees, estimateFee*1e8)
+		// #nosec G701 always in range
+		fees = big.NewInt(int64(estimateFee * 1e8))
+	}
 
 	// calculate remaining btc to TSS self
 	tssAddrWPKH := signer.tssSigner.BTCAddressWitnessPubkeyHash()
@@ -253,8 +268,9 @@ func (signer *BTCSigner) TryProcessOutTx(send *types.CrossChainTx, outTxMan *Out
 		return
 	}
 
+	sizelimit := params.OutboundTxGasLimit
 	gasprice, ok := new(big.Int).SetString(params.OutboundTxGasPrice, 10)
-	if !ok {
+	if !ok || gasprice.Cmp(big.NewInt(0)) < 0 {
 		logger.Error().Msgf("cannot convert gas price  %s ", params.OutboundTxGasPrice)
 		return
 	}
@@ -273,7 +289,7 @@ func (signer *BTCSigner) TryProcessOutTx(send *types.CrossChainTx, outTxMan *Out
 
 	logger.Info().Msgf("SignWithdrawTx: to %s, value %d sats", addr.EncodeAddress(), params.Amount.Uint64())
 	logger.Info().Msgf("using utxos: %v", btcClient.utxos)
-	tx, err := signer.SignWithdrawTx(to, float64(params.Amount.Uint64())/1e8, gasprice, btcClient, height,
+	tx, err := signer.SignWithdrawTx(to, float64(params.Amount.Uint64())/1e8, gasprice, sizelimit, btcClient, height,
 		outboundTxTssNonce, &btcClient.chain)
 	if err != nil {
 		logger.Warn().Err(err).Msgf("SignOutboundTx error: nonce %d chain %d", outboundTxTssNonce, params.ReceiverChainId)