How can I accurately anticipate wire transfer fees from intermediary banks?

Your question asks how to prove a negative, and that's not possible.

The assumption that there are 'extra' fees popping up is based on rumors, and probably incorrect. Yes, it is sometimes difficult to find all fees listed in the fine print of the bank's fee schedules, but it is not impossible; and banks don't change their fee schedule five seconds after you send a wire, just to get you.

I have sent dozens of international wires between several major US banks and varying European banks, and have rarely encountered any surprise fees (and they were my fault, for not reading the fee schedule). For example, JPMorgan Chase and Bank of America do not charge more than the ~40$ flat they list in their fee schedule (for online submittal - in person or on the phone is higher).

One important point is to chose 'SPLIT' for the fees, meaning that each bank takes their fee themselves; that is typically cheapest, as they are both locked to their fee schedule. If you chose either bank to handle all fees, they likely take a huge chunk, pay the remote fees, and keep the rest 'for their efforts'.

Another critical thing to watch for is the currency conversion - most banks are eager to convert for you, and use an 'adjusted' conversion ratio, which gives them a painful chunk of your money. Read both banks' details about it, before you decide.
My experience is that it is best to let the receiver do the currency conversion and get the exact market exchange ratio, with no fees at all; but that might not apply to all cases.

Here a list of potential fees (read the fee schedule to find if either bank has them, and how much they are):

• sending bank's 'outgoing wire transfer fee'. Varies probably depending on how you request it, online typical cheapest.
• receiving bank's 'incoming wire transfer fee'. Can be even zero, should be generally lower than the outgoing fee.
• currency conversion fee. Typically, higher at the sending bank, often zero at the receiving bank. This is the worst piece for large amounts of money, because it is a percentage, not a flat amount.
• intermediary bank's 'handling fee'. If either of the banks has no international presence/activity, it will need to use an intermediary, and they take a fee (worst case, both sides need one, so two fees). I have seen 20$ for this, but it could be anything. This part is hardest to know upfront, as the sending bank won't tell you whom they work with, and they often have no idea what it will cost - it doesn't matter to them. This fee can be avoided by using larger banks.

Here is the answer I've received from one of the major international money transfer services in reply to my question about intermediary fees.

Depending on what route the payment takes and the relationship between the correspondent banks, an intermediary bank and/or the receiving bank may deduct a fee from the payment amount, prior to crediting funds to the beneficiary account. This fee can vary in amount and we cannot predict whether it will occur or, if it does, what amount will be deducted.

This is not a comprehensive answer to your question, just an anecdotal one, but maybe it can shed some light nonetheless.