If you want to know how many British Pounds you would get for 100 US Dollars or vice versa you can get a fair idea on the many conversion sites on the Internet. However, it is vital that you know that these conversion rates aren`t the same as the ones that the bank charges. This applies whether you change your monies in a bank or pay with your credit card.
The conversion rates on the Internet are updated regularly whereas the exchange rates that you will pay are set on a daily basis. Additionally, the banks and the exchange rate boots will set their own buy and sell rate so that they will make a profit of the transaction. On top of that, if you buy something with your credit card whilst abroad your credit card company usually adds a transaction fee, normally 1-2%.
If you are looking for an overview and to get a feel for what your money is worth then there are many sites that have their own currency converter. Some are more accurate and used more widely than others. Here are a few sites that are good and that I know businesses are using etc;
~ Oanda – http://www.oanda.com
~ XE – http://www.xe.com/ucc
~ X-rates – http://www.x-rates.com/calculator.html
These sites are fairly similar and I have ranked them the way I would use and recommend them. They are all easy to use and will get you a number very quickly. They have drop down menus and it is very easy to change the amounts etc.
On the other hand, if you want a better understanding as to how much money you will receive when changing your currency for another, use the homepages of Banks and financial institutions. Many banks have their buy and sell rate on their webpage and that is the rate they are offering for the day. Additionally, do keep in mind that some will change a commission and so you might receive a little less than anticipated.
Another alternative is to have a look the site where you perhaps are thinking of buying an item. If it an American website the item might be priced in US Dollars but often there is a button where you can convert into another currency. Bear in mind though that this is the rate of this site and might not correspond to the rate that your credit card company is charging at the moment.
Often what is relevant is the ratio of one particular currency in relation to another. That way you will be able to quickly calculate what something costs when you are abroad. Say for example that you get 2 US Dollars for every British Pound. You then have a 2:1 ratio. If you then you go to the States and your meal costs USD 40, you can quickly convert it into British Pounds, 20. You always divide the price in 2.