Total cost = phone price + monthly bill * contract duration Once you know all of these values, the total expenses on your cell phone (provided you buy it outright) can be expressed by the following equation: The monthly expenses on your cell phone bill. If you plan to get a used one for a lower price or get your phone from a different continent at a high shipping cost, you should include all of these discounts or extra costs here. This figure should be as close to reality as possible it is the retail price at which you will purchase your new phone. Most of us change our phones after about two years, but if you buy a new model each year or stick to the old one for longer, feel free to change this number as you wish.

Treat this value as the number of months after which you are likely to replace your phone. Technically, you will not sign any contract with the carrier if you'll be using pre-paid cards. The first step is estimating what will be the total expenses for your phone if you choose to buy it at Amazon or at Walmart.

Calculator mobile phone