diff --git a/supporting-docs/projects/2016-02-10-synapse.md b/supporting-docs/projects/2016-02-10-synapse.md
index 944c2715..d29b2c36 100644
--- a/supporting-docs/projects/2016-02-10-synapse.md
+++ b/supporting-docs/projects/2016-02-10-synapse.md
@@ -25,3 +25,5 @@ Martin Giess has created an auto-deployment process with vagrant/ansible, tested
 Synapse is also on the [Open Build Service](https://obs.infoserver.lv/project/show/matrix-synapse).
 
 Finally, a Synapse package is available for the [Nix package manager](https://github.com/NixOS/nixpkgs/blob/master/nixos/modules/services/misc/matrix-synapse.nix).
+
+There is also a [handy spreadsheet](http://matrix.org/docs/projects/other/hdd-space-calc-for-synapse.html) to calculate HDD space for your Synapse instance.