Currency conversion takes just a few simple steps. To do a theoretical currency conversion, you need a simple mathematical equation. For example, if the conversion rate is .014 pounds sterling per rupee, then the conversion equation is 1 rupee x .014 pounds sterling/rupee = .014 pounds sterling. When converting multiple rupees to pounds sterling, adjust the equation accordingly. Actual paper money can be exchanged anywhere that does currency conversions; it could be an airport, a bank or a money-exchange stand in a city.
Open a currency conversion website such as CoinMill, Oanda or XE to convert your rupees to pounds mathematically.
Multiply one rupee by the number of pounds sterling equivalent to one rupee according to the day's exchange rate. With this method you will determine the value of pounds sterling against one rupee. Use a calculator to check your calculations if you are converting multiple rupees to pounds sterling.
Visit a money-exchange location such as a currency conversion stand in an international airport---in Britain, India or another location---or a bank in order to convert actual rupees to pounds sterling. Money-exchange businesses in cities in either country will also convert currency, as will Western Union locations. Use your calculator to make sure that you have received correct change.
Currency conversions are subject to change as the markets change. The conversion rate one day will not be the conversion rate the next day. Keep checking the conversion rates during your trip so that you know how many rupees you will be getting per pound sterling. The market may fluctuate, so you may find that the pound sterling is worth more or less from one day to the next. Some money changers---such as airports---charge large commissions on such transactions. In order to avoid these, find a place that says "no commission" or use an ATM to withdraw rupees from your British account. Withdrawing a foreign currency from an ATM will usually come with a small fee, but it will be less than the commission taken by an airport.
What may seem like small fluctuations in the conversion rate might make a big difference in the worth of either currency. A change in a tenth of a point on the rupee may greatly affect the number of rupees that you get per pound sterling. Since there are multiple rupees per pound sterling, British account-holders will likely find India to be quite cheap. However, when exchanging money in the reverse, you will lose money because the conversion rate for rupees to pounds will not be the same as the conversion rate for pounds to rupees.