diff --git a/core/types/block.go b/core/types/block.go
index ffe3173427..92b868d9da 100644
--- a/core/types/block.go
+++ b/core/types/block.go
@@ -25,6 +25,7 @@ import (
 	"sort"
 	"sync/atomic"
 	"time"
+	"unsafe"
 
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/common/hexutil"
@@ -121,6 +122,12 @@ func (h *Header) HashNoNonce() common.Hash {
 	})
 }
 
+// Size returns the approximate memory used by all internal contents. It is used
+// to approximate and limit the memory consumption of various caches.
+func (h *Header) Size() common.StorageSize {
+	return common.StorageSize(unsafe.Sizeof(*h)) + common.StorageSize(len(h.Extra)+(h.Difficulty.BitLen()+h.Number.BitLen()+h.Time.BitLen())/8)
+}
+
 func rlpHash(x interface{}) (h common.Hash) {
 	hw := sha3.NewKeccak256()
 	rlp.Encode(hw, x)
@@ -322,6 +329,8 @@ func (b *Block) HashNoNonce() common.Hash {
 	return b.header.HashNoNonce()
 }
 
+// Size returns the true RLP encoded storage size of the block, either by encoding
+// and returning it, or returning a previsouly cached value.
 func (b *Block) Size() common.StorageSize {
 	if size := b.size.Load(); size != nil {
 		return size.(common.StorageSize)
diff --git a/core/types/receipt.go b/core/types/receipt.go
index 208d54aaa1..f945f6f6a2 100644
--- a/core/types/receipt.go
+++ b/core/types/receipt.go
@@ -20,6 +20,7 @@ import (
 	"bytes"
 	"fmt"
 	"io"
+	"unsafe"
 
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/common/hexutil"
@@ -136,6 +137,18 @@ func (r *Receipt) statusEncoding() []byte {
 	return r.PostState
 }
 
+// Size returns the approximate memory used by all internal contents. It is used
+// to approximate and limit the memory consumption of various caches.
+func (r *Receipt) Size() common.StorageSize {
+	size := common.StorageSize(unsafe.Sizeof(*r)) + common.StorageSize(len(r.PostState))
+
+	size += common.StorageSize(len(r.Logs)) * common.StorageSize(unsafe.Sizeof(Log{}))
+	for _, log := range r.Logs {
+		size += common.StorageSize(len(log.Topics)*common.HashLength + len(log.Data))
+	}
+	return size
+}
+
 // String implements the Stringer interface.
 func (r *Receipt) String() string {
 	if len(r.PostState) == 0 {
diff --git a/core/types/transaction.go b/core/types/transaction.go
index a7ed211e42..5660582baf 100644
--- a/core/types/transaction.go
+++ b/core/types/transaction.go
@@ -206,6 +206,8 @@ func (tx *Transaction) Hash() common.Hash {
 	return v
 }
 
+// Size returns the true RLP encoded storage size of the transaction, either by
+// encoding and returning it, or returning a previsouly cached value.
 func (tx *Transaction) Size() common.StorageSize {
 	if size := tx.size.Load(); size != nil {
 		return size.(common.StorageSize)
diff --git a/eth/downloader/queue.go b/eth/downloader/queue.go
index 8b72375204..a1a70e46ea 100644
--- a/eth/downloader/queue.go
+++ b/eth/downloader/queue.go
@@ -28,7 +28,6 @@ import (
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/core/types"
 	"github.com/ethereum/go-ethereum/log"
-	"github.com/ethereum/go-ethereum/rlp"
 	"github.com/rcrowley/go-metrics"
 	"gopkg.in/karalabe/cookiejar.v2/collections/prque"
 )
@@ -386,13 +385,16 @@ func (q *queue) Results(block bool) []*fetchResult {
 
 		// Recalculate the result item weights to prevent memory exhaustion
 		for _, result := range results {
-			var size common.StorageSize
-
-			blob, _ := rlp.EncodeToBytes(result.Receipts) // TODO(karalabe): Whoah, nice hack, super optimal
-			size += common.StorageSize(len(blob))
-			blob, _ = rlp.EncodeToBytes(result.Transactions)
-			size += common.StorageSize(len(blob))
-
+			size := result.Header.Size()
+			for _, uncle := range result.Uncles {
+				size += uncle.Size()
+			}
+			for _, receipt := range result.Receipts {
+				size += receipt.Size()
+			}
+			for _, tx := range result.Transactions {
+				size += tx.Size()
+			}
 			q.resultSize = common.StorageSize(blockCacheSizeWeight)*size + (1-common.StorageSize(blockCacheSizeWeight))*q.resultSize
 		}
 	}