# OIS fixed rate compunding criteria

I have the following doubt: How should the OIS fixed rate be considered in computing principal+interests at the maturity of the swap? I mean, if i.e. the swap lasts 4 day (without w.e. in the middle), and the day count convention is ACT/365, I've found both: P*(1+OIS*4/365) (here) and P*(1+OIS/365)^4 (here)

Thanks!

Depends on which OIS you are referring to. For EUR OIS Swaps, the EONIA Swap rate is calculated via the usual compounding formula (notice that in the example below, the rate $$r_i$$ is updated every night):