Sicyon calculator
Sicyon is a freeware sci/eng all-in-one software tool - expression calculator, constant database, unit converter, solver
20 Alternatives To Sicyon calculator

CALCU
CALCU is a simple, yet beautiful and powerful calculator.
Calcbot for Apple Watch
Calculate, convert, and split tips from your wrist

Calculator plus1
The calculator with the basic mathematical functions for pupils and students
Getcalc
getcalc.com - online calculators, formulas & work with steps (step by step calculation) for expressions, statistics, probability, finance, health, geometry, general purpose & engineering calculations along with basic & scientific calculators.

Gnome calculator
Calculator for the GNOME Desktop Environment, formerly known as gcalc (and gcalctool CLI).

Insect
High precision scientific calculator with full support for physical units.
Numi
Numi Organic Tea is a premium, Fair Trade sustainable company specializing in unique and innovative blends of green, black, white, oolong teas, Pu-erh, rooibos, herbal and Flowering Tea™.

PCalc
PCalc is the powerful choice for scientists, engineers, students, programmers, or indeed anybody…

SpeedCrunch
SpeedCrunch. SpeedCrunch is a high-precision scientific calculator featuring a fast, keyboard-driven user interface. It is free and open-source software, licensed under the GPL. Download Documentation Donate .

WebMath
WebMath is a math site that creates answers to particular math inquiries and issues, as entered by a client, at a precise minute.
WolframAlpha
WolframAlpha brings expert-level knowledge and capabilities to the broadest possible range of people—spanning all professions and education levels.
fxSolver
fxSolver is an free online math solver, equation library, graphing calculator and science/engineering problem helper. To get started, add some formulas, fill in any input variables and press “Solve.”
galculator
galculator is an open source scientific calculator with a modern GUI and a wide range of operation modes. It supports algebraic, reverse polish (RPN) and paper mode notations.
handyCalc
Solve things in your hand.