diff --git a/README.rst b/README.rst
index 12f0c0c51a..4491b45181 100644
--- a/README.rst
+++ b/README.rst
@@ -359,7 +359,7 @@ https://www.archlinux.org/packages/community/any/matrix-synapse/, which should p
 the necessary dependencies. If the default web client is to be served (enabled by default in
 the generated config),
 https://www.archlinux.org/packages/community/any/python2-matrix-angular-sdk/ will also need to
-be installed. 
+be installed.
 
 Alternatively, to install using pip a few changes may be needed as ArchLinux
 defaults to python 3, but synapse currently assumes python 2.7 by default:
@@ -899,12 +899,9 @@ cache a lot of recent room data and metadata in RAM in order to speed up
 common requests.  We'll improve this in future, but for now the easiest
 way to either reduce the RAM usage (at the risk of slowing things down)
 is to set the almost-undocumented ``SYNAPSE_CACHE_FACTOR`` environment
-variable.  Roughly speaking, a SYNAPSE_CACHE_FACTOR of 1.0 will max out
-at around 3-4GB of resident memory - this is what we currently run the
-matrix.org on.  The default setting is currently 0.1, which is probably
-around a ~700MB footprint.  You can dial it down further to 0.02 if
-desired, which targets roughly ~512MB.  Conversely you can dial it up if
-you need performance for lots of users and have a box with a lot of RAM.
+variable.  The default is 0.5, which can be decreased to reduce RAM usage
+in memory constrained enviroments, or increased if performance starts to
+degrade.
 
 
 .. _`key_management`: https://matrix.org/docs/spec/server_server/unstable.html#retrieving-server-keys
diff --git a/synapse/state.py b/synapse/state.py
index 5b386e3183..390799fbd5 100644
--- a/synapse/state.py
+++ b/synapse/state.py
@@ -24,13 +24,13 @@ from synapse.api.constants import EventTypes
 from synapse.api.errors import AuthError
 from synapse.events.snapshot import EventContext
 from synapse.util.async import Linearizer
+from synapse.util.caches import CACHE_SIZE_FACTOR
 
 from collections import namedtuple
 from frozendict import frozendict
 
 import logging
 import hashlib
-import os
 
 logger = logging.getLogger(__name__)
 
@@ -38,9 +38,6 @@ logger = logging.getLogger(__name__)
 KeyStateTuple = namedtuple("KeyStateTuple", ("context", "type", "state_key"))
 
 
-CACHE_SIZE_FACTOR = float(os.environ.get("SYNAPSE_CACHE_FACTOR", 0.1))
-
-
 SIZE_OF_CACHE = int(100000 * CACHE_SIZE_FACTOR)
 EVICTION_TIMEOUT_SECONDS = 60 * 60
 
diff --git a/synapse/storage/_base.py b/synapse/storage/_base.py
index 51730a88bf..6f54036d67 100644
--- a/synapse/storage/_base.py
+++ b/synapse/storage/_base.py
@@ -16,6 +16,7 @@ import logging
 
 from synapse.api.errors import StoreError
 from synapse.util.logcontext import LoggingContext, PreserveLoggingContext
+from synapse.util.caches import CACHE_SIZE_FACTOR
 from synapse.util.caches.dictionary_cache import DictionaryCache
 from synapse.util.caches.descriptors import Cache
 from synapse.storage.engines import PostgresEngine
@@ -27,10 +28,6 @@ from twisted.internet import defer
 import sys
 import time
 import threading
-import os
-
-
-CACHE_SIZE_FACTOR = float(os.environ.get("SYNAPSE_CACHE_FACTOR", 0.1))
 
 
 logger = logging.getLogger(__name__)
diff --git a/synapse/storage/client_ips.py b/synapse/storage/client_ips.py
index 88a5eb232f..fc468ea185 100644
--- a/synapse/storage/client_ips.py
+++ b/synapse/storage/client_ips.py
@@ -20,7 +20,8 @@ from twisted.internet import defer, reactor
 from ._base import Cache
 from . import background_updates
 
-import os
+from synapse.util.caches import CACHE_SIZE_FACTOR
+
 
 logger = logging.getLogger(__name__)
 
@@ -30,9 +31,6 @@ logger = logging.getLogger(__name__)
 LAST_SEEN_GRANULARITY = 120 * 1000
 
 
-CACHE_SIZE_FACTOR = float(os.environ.get("SYNAPSE_CACHE_FACTOR", 0.1))
-
-
 class ClientIpStore(background_updates.BackgroundUpdateStore):
     def __init__(self, hs):
         self.client_ip_last_seen = Cache(
diff --git a/synapse/util/caches/__init__.py b/synapse/util/caches/__init__.py
index 4a83c46d98..4adae96681 100644
--- a/synapse/util/caches/__init__.py
+++ b/synapse/util/caches/__init__.py
@@ -16,7 +16,7 @@
 import synapse.metrics
 import os
 
-CACHE_SIZE_FACTOR = float(os.environ.get("SYNAPSE_CACHE_FACTOR", 0.1))
+CACHE_SIZE_FACTOR = float(os.environ.get("SYNAPSE_CACHE_FACTOR", 0.5))
 
 metrics = synapse.metrics.get_metrics_for("synapse.util.caches")
 
diff --git a/synapse/util/caches/descriptors.py b/synapse/util/caches/descriptors.py
index cbdff86596..af65bfe7b8 100644
--- a/synapse/util/caches/descriptors.py
+++ b/synapse/util/caches/descriptors.py
@@ -16,6 +16,7 @@ import logging
 
 from synapse.util.async import ObservableDeferred
 from synapse.util import unwrapFirstError, logcontext
+from synapse.util.caches import CACHE_SIZE_FACTOR
 from synapse.util.caches.lrucache import LruCache
 from synapse.util.caches.treecache import TreeCache, iterate_tree_cache_entry
 from synapse.util.stringutils import to_ascii
@@ -25,7 +26,6 @@ from . import register_cache
 from twisted.internet import defer
 from collections import namedtuple
 
-import os
 import functools
 import inspect
 import threading
@@ -37,9 +37,6 @@ logger = logging.getLogger(__name__)
 _CacheSentinel = object()
 
 
-CACHE_SIZE_FACTOR = float(os.environ.get("SYNAPSE_CACHE_FACTOR", 0.1))
-
-
 class CacheEntry(object):
     __slots__ = [
         "deferred", "sequence", "callbacks", "invalidated"
diff --git a/synapse/util/caches/stream_change_cache.py b/synapse/util/caches/stream_change_cache.py
index 609625b322..941d873ab8 100644
--- a/synapse/util/caches/stream_change_cache.py
+++ b/synapse/util/caches/stream_change_cache.py
@@ -13,20 +13,16 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-from synapse.util.caches import register_cache
+from synapse.util.caches import register_cache, CACHE_SIZE_FACTOR
 
 
 from blist import sorteddict
 import logging
-import os
 
 
 logger = logging.getLogger(__name__)
 
 
-CACHE_SIZE_FACTOR = float(os.environ.get("SYNAPSE_CACHE_FACTOR", 0.1))
-
-
 class StreamChangeCache(object):
     """Keeps track of the stream positions of the latest change in a set of entities.
 
diff --git a/tests/storage/test__base.py b/tests/storage/test__base.py
index 281eb16254..3cfa21c9f8 100644
--- a/tests/storage/test__base.py
+++ b/tests/storage/test__base.py
@@ -241,7 +241,7 @@ class CacheDecoratorTestCase(unittest.TestCase):
         callcount2 = [0]
 
         class A(object):
-            @cached(max_entries=20)  # HACK: This makes it 2 due to cache factor
+            @cached(max_entries=4)  # HACK: This makes it 2 due to cache factor
             def func(self, key):
                 callcount[0] += 1
                 return key