If you asked five educators, each from a different state, what their opinion of calculator usage on standardized tests is, there's a good chance you would get five different answers. Up to this point, each state has individually set guidelines for how and when students are able to use calculators on the tests.
But now, with such a large number of states adopting either the PARCC or Smarter Balanced assessment consortiums to test Common Core math standards understanding, the calculator usage guidelines are going to become much more uniform from statetostate. With this in mind, Erik W. Robelen of Education Week recently posted an indepth blog post detailing what each state (that adopted and stuck with the Common Core math standards) can expect regarding calculator ground rules. Below is the 'cliff notes' version of what you can expect regarding calculator usage from each test.
The Common Core Assessment Calculator Breakdown
Below, I've broken the calculator guideline information provided by the two testing consortiums (and from the Education Week blog post) into two sections: 'Similarities between PARCC and Smarter Balanced' and 'Differences between PARCC and Smarter Balanced'.

Similarities between PARCC and Smarter Balanced:
 Both assessments restrict calculator usage on the grade 35 tests
 On grades 6 and above, there will be calculator "on" sections and calculator "off" sections, depending on what math functionalities are involved/required
 Both allow for the use of a graphing calculator (like a Texas Instruments TI84 or similar model) at the high school level (and only the high school level)
 Both also intend to provide an online graphing calculator to students taking the online version of the assessments

Differences between PARCC and Smarter Balanced:
 The middle school requirements vary significantly between the two tests.
 PARCC: grade 67 students must use a four function calculator, grade 8 students can use a scientific calculator
 Smarter Balanced: grade 6 students can only use a four function calculator, grade 78 students can use a scientific calculator
 Smarter Balanced does not allow handheld calculator use for students taking the online version of the test.
 PARCC allows handheld calculator usage for both the paper version and the online version (for 20142015 testing year, will reassess following first year).
 Here is a graphical breakdown of what type of calculator each assessment allows per grade level (image from Education Week):
Questions Still Loom Regarding Calculator Usage and Fairness
Though the calculator usage picture is becomming more clear, educators still raise many valid questions, including:
 When specifically are students able to use the devices and what students are elligible for accomodations?
 Are educators responsible for providing calculator training (in addition to the alreadyestablished math curriculum)?
 Do students who are more adept with calculators have an advantage?
 Are schools required to provide calculators to students who do not bring their own/Should schools allow students to bring calculators from home?