Find out the day's exchange rate by calling a bank or going online. Enter "currency exchange" or "pounds to euros" in the search field.
Multiply the number of pounds by the day's exchange rate. If 1 pound is worth 1.19 euros, 100 pounds is worth 119 euros.
Visit an online currency converter that will do the computation automatically (see Resources).
Take your British pounds to a currency exchange booth, located in all international airports. The clerk will calculate the conversion based on the day's rate of exchange. Expect to pay handling and transaction fees.
Check the Yellow Pages under "Currency Exchange" if you are making your exchange in the United States. Call to inquire whether it has euros on hand.
Take your pounds to a bank and ask to have them exchanged for euros. Banks around the world exchange currencies. If the bank is in a small town, call first to make sure it has euros on hand.