diff --git a/changelog.d/16219.feature b/changelog.d/16219.feature
new file mode 100644
index 0000000000..c789f2abb7
--- /dev/null
+++ b/changelog.d/16219.feature
@@ -0,0 +1 @@
+Add the ability to use `G` (GiB) and `T` (TiB) suffixes in configuration options that refer to numbers of bytes.
\ No newline at end of file
diff --git a/docs/usage/configuration/config_documentation.md b/docs/usage/configuration/config_documentation.md
index 0b1725816e..97fd1beb39 100644
--- a/docs/usage/configuration/config_documentation.md
+++ b/docs/usage/configuration/config_documentation.md
@@ -25,8 +25,10 @@ messages from the database after 5 minutes, rather than 5 months.
 
 In addition, configuration options referring to size use the following suffixes:
 
-* `M` = MiB, or 1,048,576 bytes
 * `K` = KiB, or 1024 bytes
+* `M` = MiB, or 1,048,576 bytes
+* `G` = GiB, or 1,073,741,824 bytes
+* `T` = TiB, or 1,099,511,627,776 bytes
 
 For example, setting `max_avatar_size: 10M` means that Synapse will not accept files larger than 10,485,760 bytes
 for a user avatar.
diff --git a/synapse/config/_base.py b/synapse/config/_base.py
index 69a8318127..58856839e1 100644
--- a/synapse/config/_base.py
+++ b/synapse/config/_base.py
@@ -179,8 +179,9 @@ class Config:
 
         If an integer is provided it is treated as bytes and is unchanged.
 
-        String byte sizes can have a suffix of 'K' or `M`, representing kibibytes and
-        mebibytes respectively. No suffix is understood as a plain byte count.
+        String byte sizes can have a suffix of 'K', `M`, `G` or `T`,
+        representing kibibytes, mebibytes, gibibytes and tebibytes respectively.
+        No suffix is understood as a plain byte count.
 
         Raises:
             TypeError, if given something other than an integer or a string
@@ -189,7 +190,7 @@ class Config:
         if type(value) is int:  # noqa: E721
             return value
         elif isinstance(value, str):
-            sizes = {"K": 1024, "M": 1024 * 1024}
+            sizes = {"K": 1024, "M": 1024 * 1024, "G": 1024**3, "T": 1024**4}
             size = 1
             suffix = value[-1]
             if suffix in sizes: