# How do I calculate the inverse rate of an exotic? [closed]

I'm getting my FX rate information from a provider that only provides me one direction THB => CHF.

Now I want to calculate the inverse: CHF => THB.

I see two possibilities:

1. Take the middle of the rate THB => CHF and compute the inverse
2. Go over the USD: CHF => USD => THB

What is the correct way? Consider two scenarios:

1. I only want the middle of the rate
2. I want the bid and ask
• Downvoters, please give me a reason why. – Roland Feb 27 '17 at 8:15
• What do you want, the FX Rate or the price of an exotic option involving the FX rate of CHF-THB¿ – arodrisa Feb 27 '17 at 8:55
• @arodrisa I want the FX Rate – Roland Feb 27 '17 at 9:18
• I voted to close as basic financial questions are off-topic for this site (I did not downvote though). – Chris Taylor Feb 28 '17 at 10:47
• If you have the bid and the ask, then you just take the inverse of both and then switch the two numbers. $[a,b] \rightarrow [1/b,1/a]$ – Alex C Feb 28 '17 at 23:46