diff --git a/pkg/core/transaction/claim.go b/pkg/core/transaction/claim.go
index ecb7f0720..0b5418506 100644
--- a/pkg/core/transaction/claim.go
+++ b/pkg/core/transaction/claim.go
@@ -42,3 +42,11 @@ func (tx *ClaimTX) EncodeBinary(w io.Writer) error {
 	}
 	return nil
 }
+
+func (tx *ClaimTX) Size() int {
+	sz := util.GetVarSize(uint64(len(tx.Claims)))
+	for _, claim := range tx.Claims {
+		sz += claim.Size()
+	}
+	return sz
+}
diff --git a/pkg/core/transaction/contract.go b/pkg/core/transaction/contract.go
index 7e4cee6ac..3bcde6d37 100644
--- a/pkg/core/transaction/contract.go
+++ b/pkg/core/transaction/contract.go
@@ -23,3 +23,7 @@ func (tx *ContractTX) DecodeBinary(r io.Reader) error {
 func (tx *ContractTX) EncodeBinary(w io.Writer) error {
 	return nil
 }
+
+func (tx *ContractTX) Size() int {
+	return 0
+}
diff --git a/pkg/core/transaction/enrollment.go b/pkg/core/transaction/enrollment.go
index e43b92481..884525afe 100644
--- a/pkg/core/transaction/enrollment.go
+++ b/pkg/core/transaction/enrollment.go
@@ -26,3 +26,7 @@ func (tx *EnrollmentTX) DecodeBinary(r io.Reader) error {
 func (tx *EnrollmentTX) EncodeBinary(w io.Writer) error {
 	return tx.PublicKey.EncodeBinary(w)
 }
+
+func (tx *EnrollmentTX) Size() int {
+	return len(tx.PublicKey.Bytes())
+}
diff --git a/pkg/core/transaction/invocation.go b/pkg/core/transaction/invocation.go
index 2a0a73fcd..54de3fb00 100644
--- a/pkg/core/transaction/invocation.go
+++ b/pkg/core/transaction/invocation.go
@@ -53,3 +53,11 @@ func (tx *InvocationTX) EncodeBinary(w io.Writer) error {
 	}
 	return bw.Err
 }
+
+func (tx *InvocationTX) Size() int {
+	sz := util.GetVarSize(tx.Script)
+	if (tx.Version >= 1) {
+		sz += tx.Gas.Size()
+	}
+	return sz
+}
diff --git a/pkg/core/transaction/issue.go b/pkg/core/transaction/issue.go
index 4ad8bdec5..3a2af4e9d 100644
--- a/pkg/core/transaction/issue.go
+++ b/pkg/core/transaction/issue.go
@@ -17,3 +17,7 @@ func (tx *IssueTX) DecodeBinary(r io.Reader) error {
 func (tx *IssueTX) EncodeBinary(w io.Writer) error {
 	return nil
 }
+
+func (tx *IssueTX) Size() int {
+	return 0
+}
diff --git a/pkg/core/transaction/miner.go b/pkg/core/transaction/miner.go
index 3fa8075e9..32c41fa48 100644
--- a/pkg/core/transaction/miner.go
+++ b/pkg/core/transaction/miner.go
@@ -20,3 +20,7 @@ func (tx *MinerTX) DecodeBinary(r io.Reader) error {
 func (tx *MinerTX) EncodeBinary(w io.Writer) error {
 	return binary.Write(w, binary.LittleEndian, tx.Nonce)
 }
+
+func (tx *MinerTX) Size() int {
+	return 4 // Nonce
+}
diff --git a/pkg/core/transaction/publish.go b/pkg/core/transaction/publish.go
index f5e0a6eec..c62d91661 100644
--- a/pkg/core/transaction/publish.go
+++ b/pkg/core/transaction/publish.go
@@ -58,3 +58,16 @@ func (tx *PublishTX) DecodeBinary(r io.Reader) error {
 func (tx *PublishTX) EncodeBinary(w io.Writer) error {
 	return nil
 }
+
+func (tx *PublishTX) Size() int {
+	sz := util.GetVarSize(tx.Script) + util.GetVarSize(uint64(len(tx.ParamList)))
+	sz += 1 * len(tx.ParamList)
+	sz += 1
+	if tx.Version >= 1 {
+		sz += 1
+	}
+	sz += util.GetVarSize(tx.Name) + util.GetVarSize(tx.CodeVersion)
+	sz += util.GetVarSize(tx.Author) + util.GetVarSize(tx.Email)
+	sz += util.GetVarSize(tx.Description)
+	return sz
+}
diff --git a/pkg/core/transaction/register.go b/pkg/core/transaction/register.go
index 2d47fd442..1403e7433 100644
--- a/pkg/core/transaction/register.go
+++ b/pkg/core/transaction/register.go
@@ -62,3 +62,7 @@ func (tx *RegisterTX) EncodeBinary(w io.Writer) error {
 	bw.WriteLE(tx.Admin)
 	return bw.Err
 }
+
+func (tx *RegisterTX) Size() int {
+	return 1 + util.GetVarSize(tx.Name) + tx.Amount.Size() + 1 + len(tx.Owner.Bytes()) + tx.Admin.Size()
+}
diff --git a/pkg/core/transaction/state.go b/pkg/core/transaction/state.go
index 6bcbf8e2a..8a68c92e5 100644
--- a/pkg/core/transaction/state.go
+++ b/pkg/core/transaction/state.go
@@ -31,3 +31,11 @@ func (tx *StateTX) DecodeBinary(r io.Reader) error {
 func (tx *StateTX) EncodeBinary(w io.Writer) error {
 	return nil
 }
+
+func (tx *StateTX) Size() int {
+	sz := util.GetVarSize(uint64(len(tx.Descriptors)))
+	for _, desc := range tx.Descriptors {
+		sz += desc.Size()
+	}
+	return sz
+}
diff --git a/pkg/core/transaction/state_descriptor.go b/pkg/core/transaction/state_descriptor.go
index 95f41be52..770bb6c53 100644
--- a/pkg/core/transaction/state_descriptor.go
+++ b/pkg/core/transaction/state_descriptor.go
@@ -39,3 +39,7 @@ func (s *StateDescriptor) DecodeBinary(r io.Reader) error {
 func (s *StateDescriptor) EncodeBinary(w io.Writer) error {
 	return nil
 }
+
+func (s *StateDescriptor) Size() int {
+	return 1 + util.GetVarSize(s.Key) + util.GetVarSize(s.Value) + util.GetVarSize(s.Field)
+}
diff --git a/pkg/core/transaction/transaction.go b/pkg/core/transaction/transaction.go
index 3c2332373..32583196f 100644
--- a/pkg/core/transaction/transaction.go
+++ b/pkg/core/transaction/transaction.go
@@ -276,8 +276,7 @@ func (t *Transaction) Size() int {
 	outputSize := util.GetVarSize(t.Outputs)
 	witnesSize := util.GetVarSize(t.Scripts)
 	// uint8 + uint8 + attrSize + inputSize + outputSize + witnesSize
-	return 2 + attrSize + inputSize + outputSize + witnesSize
-
+	return 2 + attrSize + inputSize + outputSize + witnesSize + t.Data.Size()
 }
 
 // Bytes convert the transaction to []byte
diff --git a/pkg/core/transaction/txer.go b/pkg/core/transaction/txer.go
index 0134f15fb..e87187bfd 100644
--- a/pkg/core/transaction/txer.go
+++ b/pkg/core/transaction/txer.go
@@ -7,4 +7,5 @@ import "io"
 type TXer interface {
 	DecodeBinary(io.Reader) error
 	EncodeBinary(io.Writer) error
+	Size() int
 }