The answer to your question is that it depends upon the weight of what is being sent, and what you write on the envelope, have a look at the link that I posted and my response to it, which is about two-thirds of the way down the page. That tells you how to do it for less, and how to work out how many IRCs you'll need.

At the moment, I can't trade stamps, so IRCs are my only option.
This is the size envelope that I am making my SAE:
http://likethatprice.com/wp-content/uploads/wpsc/product_images/koleimports/OP299.jpg

Like I said, I am inserting a thin piece of cardboard to prevent bending, and then two photos. About how many stamps would that need to be sent from the UK to the US, so I know how many IRCs to purchase?

That won't be enough to get an envelope that size back to you, unless the celeb pays for extra stamps you won't get it back again.

I posted a quite full explanation of how many you will need, and how you can get something that weight back a bit cheaper here http://www.fanmail.biz/mboard/viewtopic.php?f=2&t=228553

I normally enclose 2 if writing to the states.

Tip: If you're concerned about lack of return postage enclosed, mention it in your letter. You stand a better chance of the recipient adding to it and getting your response back to you. Shows you tried. ;-)

Just a tip: try getting UK stamps by trading etc. That will increase your chances of getting a reply! Good Luck!:)

[quote="Jack5555"]I live in the US, and I have sent/plan on sending LOR with SAE to various Harry Potter actors in the UK. I was wondering, is one IRC enough if I enclose a SAE that is 9x6, with a thin piece of cardboard in it to prevent bending (like cereal box thin)? I want to have the highest chance possible of getting a response.
If I decide to order British stamps and use those in the future, about how many should I use for an envelope that size?[/quote]

Sending to UK, using an IRC is not that worthy... the weight available of one is only 10g..

About the stamp, 10g=67p and 20g=110p I am not sure about the weight of the size that you talked about.. You can estimate by yourself..

Hope this helps

I live in the US, and I have sent/plan on sending LOR with SAE to various Harry Potter actors in the UK. I was wondering, is one IRC enough if I enclose a SAE that is 9x6, with a thin piece of cardboard in it to prevent bending (like cereal box thin)? I want to have the highest chance possible of getting a response.
If I decide to order British stamps and use those in the future, about how many should I use for an envelope that size?