diff --git a/Cargo.toml b/Cargo.toml
index 13295f766..4d23f49f8 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -20,6 +20,7 @@ lazy_static = "0.1.*"
 secp256k1 = "0.5.1"
 rust-crypto = "0.2.34"
 elastic-array = "0.4"
+heapsize = "0.2"
 
 [dev-dependencies]
 json-tests = { path = "json-tests" }
diff --git a/src/heapsizeof.rs b/src/heapsizeof.rs
new file mode 100644
index 000000000..c6d4cace4
--- /dev/null
+++ b/src/heapsizeof.rs
@@ -0,0 +1,5 @@
+use uint::*;
+use hash::*;
+
+known_heap_size!(0, H32, H64, H128, Address, H256, H264, H512, H520, H1024, H2048);
+known_heap_size!(0, U128, U256);
diff --git a/src/lib.rs b/src/lib.rs
index 24b404a88..9120f0977 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -32,10 +32,14 @@ extern crate mio;
 extern crate rand;
 extern crate rocksdb;
 extern crate tiny_keccak;
+
+#[macro_use]
+extern crate heapsize;
 #[macro_use]
 extern crate log;
 #[macro_use]
 extern crate lazy_static;
+
 extern crate env_logger;
 
 extern crate time;
@@ -60,5 +64,7 @@ pub mod crypto;
 pub mod triehash;
 pub mod trie;
 pub mod nibbleslice;
+pub mod heapsizeof;
+pub mod squeeze;
 
 //pub mod network;
diff --git a/src/squeeze.rs b/src/squeeze.rs
new file mode 100644
index 000000000..e81a13793
--- /dev/null
+++ b/src/squeeze.rs
@@ -0,0 +1,67 @@
+//! Helper module that should be used to randomly squeeze 
+//! caches to a given size in bytes
+//! 
+//! ```
+//! extern crate heapsize;
+//! extern crate ethcore_util as util;
+//! use std::collections::HashMap;
+//! use std::mem::size_of;
+//! use heapsize::HeapSizeOf;
+//! use util::squeeze::Squeeze;
+//! 
+//! fn main() {
+//!     let initial_size = 60;
+//! 	let mut map: HashMap<u8, u8> = HashMap::with_capacity(initial_size);
+//! 	assert!(map.capacity() >= initial_size);
+//! 	for i in 0..initial_size {
+//! 		map.insert(i as u8, i as u8);
+//! 	}
+//! 	
+//! 	assert_eq!(map.heap_size_of_children(), map.capacity() * 2 * size_of::<u8>());
+//! 	assert_eq!(map.len(), initial_size);
+//! 	let initial_heap_size = map.heap_size_of_children();
+//!
+//! 	// squeeze it to size of key and value
+//! 	map.squeeze(2 * size_of::<u8>());
+//! 	assert_eq!(map.len(), 1);
+//! 	
+//! 	// its likely that heap size was reduced, but we can't be 100% sure
+//! 	assert!(initial_heap_size >= map.heap_size_of_children());
+//! }
+//! ```
+
+use std::collections::HashMap;
+use std::hash::Hash;
+use heapsize::HeapSizeOf;
+
+/// Should be used to squeeze collections to certain size in bytes
+pub trait Squeeze {
+	fn squeeze(&mut self, size: usize);
+}
+
+impl<K, T> Squeeze for HashMap<K, T> where K: Eq + Hash + Clone + HeapSizeOf, T: HeapSizeOf {
+	fn squeeze(&mut self, size: usize) {
+		if self.len() == 0 {
+			return
+		}
+		
+		let size_of_entry = self.heap_size_of_children() / self.capacity();
+		let all_entries = size_of_entry * self.len();
+		let mut shrinked_size = all_entries;
+
+		while self.len() > 0 && shrinked_size > size {
+			// could be optimized
+			let key = self.keys().next().unwrap().clone();
+			self.remove(&key);
+			shrinked_size -= size_of_entry;
+		}
+
+		self.shrink_to_fit();
+
+		// if we squeezed something, but not enough, squeeze again
+		if all_entries != shrinked_size && self.heap_size_of_children() > size {
+			self.squeeze(size);
+		}
+	}
+}
+