diff --git a/src/utils/formatSize.js b/src/utils/formatSize.js
new file mode 100644
index 00000000..c8a6ea1e
--- /dev/null
+++ b/src/utils/formatSize.js
@@ -0,0 +1,29 @@
+/*
+Copyright 2020 The Matrix.org Foundation C.I.C.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+export function formatSize(size, decimals = 2) {
+    if (Number.isSafeInteger(size)) {
+        const base = Math.min(3, Math.floor(Math.log(size) / Math.log(1024)));
+        const decimalFactor = Math.pow(10, decimals);
+        const formattedSize = Math.round((size / Math.pow(1024, base)) * decimalFactor) / decimalFactor;
+        switch (base) {
+            case 0: return `${formattedSize} bytes`;
+            case 1: return `${formattedSize} KB`;
+            case 2: return `${formattedSize} MB`;
+            case 3: return `${formattedSize} GB`;
+        }
+    }
+}