I can't wrap my head around how to determine the interest rates to calculate the forward rates of any currency. At this point, I don't even know if this data is actually available to do the calculation myself.
From Investing.com (link) I wish to determine the 1Y and 1M forward rate for starters. I figured out the formula:
spot rate x (1 + domestic interest rate) / (1 + foreign interest rate) and I know the spot rate, 1.08 for EUR/USD.
Now when it comes to Domestic and Foreign rates I simply do not understand what I should be using here. First, I figured it must be ESTER and SOFR. The result I get is quite similar but for anything that is not 1Y, any other duration (e.g. 1M) calculation I do just differs greatly. Then I figured Central Bank rates but in the EU it being 0% and in the US 0.5%, that didn't even come near the forward rate.
So now I am confused, how can I calculate these values if that is actually even possible?