eCalc is an online calculator that includes both basic and scientific modes. The scientific mode calculator features advanced functions such as unit conversion, constants, equation solving, decimal-to-fraction, base conversion, and handling of complex numbers. The calculators run in a web browser without special downloads, registration, or plugins. The online display features large buttons and interactive capability which allows its use in presentations. Other site materials include a demonstration video showing how the calculator works and links to reviews of actual calculators.