How our calculator works

We use your postcode to perform an availability check and identify the home phone suppliers available where you live. This also includes services provided by cable companies.

The calculator translates the usage information that you have entered into a number of calls per month to each destination (local, national, mobile and international), across each time of day (daytime, evening and weekend). Each call has a corresponding average call cost associated with it.

This average call cost is calculated by using a probability distribution around an average call duration. The probability distribution is used to determine how likely it is that each call will last a certain amount of time. From knowing this, the calculator can work out how much of your average call cost is due to the minimum call charge, and how much is due to the pence per minute rate.

Any free calls and discounts are then taken into account, as are any fixed monthly charges. The resultant monthly cost is then multiplied by 12 to give an overall annual cost.

You can opt to filter out or include plans based on the service options you require. If for example you select to only see plans using a prefix number we will filter out all plans that do not offer this option.

Your estimated current bill, the calculated annual cost and the calculated % saving are all calculated over a period of one year. Shorter or longer periods are not available.

All savings claims are based on accurate and up to date tariff information. Where we make claims on the cost of calls, this is based on the cost of certain calls with one or more suppliers compared to the cost of that call with BT Together Option 1. Where we talk about the savings that customers can make, such as 'up to £200', this is based on the actual data that users to our website input into our calculator.