The amount of data you need for a smartphone service plan depends on how -- and how often -- you use your phone. While you can use a service provider's data-estimating program to take a guess at your data consumption rate, the best way to determine how much data you need is to monitor your data usage rates and adjust your plan accordingly. Picking the wrong size data plan could lead to overage charges or paying for unused bandwidth.

Typical Data Usage

There's a good chance you can get by with 1GB a month if you use your phone's data access lightly. If you're a heavy user and occasionally stream video content, you won't need more than 4GB. According to "The Wall Street Journal's" Digits blog, the average data plan user went through 733MB a month in early 2013, and 90 percent of Verizon customers used less than 2GB of data a month.

Data Plan Estimation

If you mostly use the phone for texting and calling, you don't need a large data plan and should look at the 1GB to 2GB range. Moderate use of things like email, Web browsing, social media and apps averages around a few hundred MB of data a month each, easily falling under 1GB to 2GB data plans. However, if you plan to stream video over cellular frequently, you may need up to a 6GB monthly data plan.