diff --git a/synapse/state.py b/synapse/state.py
index 5b386e31830be80e6cfa9fec0427009a94c40277..390799fbd5815a158a2db831ad4127c0a2db7f0f 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 51730a88bf878582d4355f390d5bb69df0a93b1c..6f54036d67b37f0dc438e2c2879dcaf865f9fde2 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 88a5eb232f46d695816acd0ac71570826074151f..fc468ea18532ae7f8b35fbe8b6a07adc64ab68a3 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/descriptors.py b/synapse/util/caches/descriptors.py
index cbdff86596894a1d22103ccb97813d7dfbcc5082..af65bfe7b8095a9bc3687fbf9109dcb4738b613d 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 609625b3229656e07cc2b148be2bae7d2d76d2b4..941d873ab8019280881951dcc33444f6b5370a6c 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.