The TI-30 scientific calculator from Texas Instruments is the required calculator for most middle school math classes. TI-83 and Ti-84 are graphing calculators used in high school math classes. These calculators can be pricey. So try the free calculator downloads and graphing calculator apps available here.

TI-30 scientific calculators have function keys for algebra and algebraic equations, trigonometry, scientific math, decimal to fraction converter, unit converter, complex numbers and RPS.

http://www.eeweb.com/toolbox/download has laptop and desktop computer software for the TI-30 free.

http://education.ti.com/en/us/downloads-and-activities Texas Instruments website has free downloads for their products also. The online TI-30 scientific calculator software can be purchased for $14.95. The advantage in using online scientific calculators is that handheld are easier to lose or get stolen.

http://videomathteacher.com/free-resources/free-downloadable-math-calculators/download-free-virtual-ti-calculator-online/ This site has free math lessons and graphing calculator downloads as does this site. http://freetutorials.name/Reference1/Algebra%20tutorials%201.html

Google Play has free graphing calculator apps for Android users. https://play.google.com/store/search?q=free%20graphing%20calculator%20ti%2084&c=apps

http://appcrawlr.com/ios-apps/best-free-apps-free-graphing-calculator?price=Free&q=free+graphing+calculator&query=best-free-apps-free-graphing-calculator&deviceSeo=iphone%2Cipad&prefix=top-apps&action=seoProcess&controller=app&_rv=1 lists the best free graphing calculator apps available for any platform, from iTunes or Google Play.

If you can find a good freebie, I suggest buying an app for the iPhone, iPod or Android. This turns makes the device into a calculator and means less chance of loss or theft.