Sites and apps similar to OptiLens 3D include Wolfram Alpha, which has a free version. Other options are GeoGebra Scientific Calculator and Omni Calculator. In total there are three Calculators like OptiLens 3D for Android, iPhone and iPad.
Wolfram Alpha is a "Computational Knowledge Engine" - different from a search engine, it answers factual queries directly by computing the answer from structured data, rather than providing a list of documents or web pages that might contain the answer.
United States
Free online scientific calculator from GeoGebra: perform calculations with fractions, statistics and exponential functions, logarithms, trigonometry and much more!
Austria
EU
Omni Calculator is a web/mobile calculator that solves concrete problems such as mortgage payment, gross margin, body mass index, break-even point, etc. It's very user-friendly, flexible and usable on web, mobile and as an embeddable web widget.
PolandEU
