diff --git a/README.md b/README.md
index c248454..015fa18 100644
--- a/README.md
+++ b/README.md
@@ -44,6 +44,18 @@ platform dependent.
 The code right now can for the most part be ported to any AVR micro-controller
 with no changes.
 
+## Timings
+
+The current setup is calculated for a attiny13/a running at 4.8Mhz without the
+clock divder fuse set.
+
+This means that the actual f_cpu is 4.8Mhz to calculate the delay times
+we can use this formula:
+
+$$
+msPerOverflow = 1000ms / (\frac{4.8Mhz}{64} / 256) \aprox 6.8ms
+$$
+
 
 ## BUILDING PROJECT: