errProof is described as 'The website has a lot of useful and unique tools' and is an website in the Education & Reference category. There are more than 100 alternatives to errProof, not only websites but also apps for a variety of platforms, including Windows, Mac, Android and Linux. The best alternative is SpeedCrunch, which is both free and Open Source. Other great sites and apps similar to errProof are Wolfram Alpha (Freemium), Pastebin.com (Freemium), Qalculate! (Free, Open Source) and Write.as (Freemium, Open Source).
Complete calculus tools, easy to use and full of functions. Oficalc is, basically, a scientific calculator that may help you with mathematical calculus and that incorporates other tools to send to the highest resolution of advanced operations.
Solve is a calculator like no other! Solve solves expressions as you type and features an innovative memory system to store and recall answers. Simply touch the answer to store it and touch the stored answer to use it in an expression.
GlassCalc is a free, Windows calculator designed for quick input via keyboard. It forgoes the usual array of buttons for a single textbox where you can type an equation or mathematical expression, hit Enter, and get a result.