Either prepending or appending the IV is standard practice. The IV needs to be unique (with a given key) and for some cipher modes also needs to be unpredictable, but it does not need to be secret; sending it in plain text alongside the ciphertext is fine. If you don't have a handy way to separate the IV and ciphertext in your transmission/storage system, just putting it either before or after the ciphertext is fine as long as the recipient knows where to expect the IV to be and how long it will be.
I'm a little concerned by the mention of "calculating" the IV, though. The IV should be the output of a secure random number generator, nothing more. While there might be calculation involved in the RNG, to you it should be a black box that spits out numbers suitable for use as symmetric keys or IVs.