With the advancement of technology, calculators have become an essential tool for scientists, students, and professionals alike. Whether you need to perform complex mathematical calculations, convert units, or solve equations, having a reliable calculator at your disposal can greatly enhance your productivity. In this blog post, we will explore 17 free and open-source calculator apps that cater to the diverse needs of the scientific community.

One notable category of calculator apps is open-source calculator apps. An open-source calculator app refers to a software application whose source code is freely available for users to view, modify, and distribute. This open nature encourages collaboration, innovation, and customization within the development community.

Open-source calculator apps empower users to not only utilize the app’s existing features but also contribute to its improvement and adapt it to their specific needs.

By leveraging the collective knowledge and expertise of developers worldwide, open-source calculator apps offer a wide range of functionalities and customization options.

Users can benefit from advanced mathematical calculations, unit conversions, date calculations, statistical analysis, and much more. Additionally, open-source calculator apps often prioritize user privacy and security, as their transparent code allows for thorough scrutiny and identification of potential vulnerabilities.

In the following sections, we will delve into 17 remarkable free and open-source calculator apps that have gained popularity among scientists, students, and professionals. These apps not only provide powerful calculation capabilities but also foster an environment of collaboration and continuous improvement. Let’s explore the world of open-source calculator apps and discover the possibilities they offer.s

## 1- Qalculate

Qalculate! is a powerful and versatile cross-platform desktop calculator that offers a wide range of features, including customizable functions, unit conversion, symbolic calculations, plotting, and a user-friendly interface.

### Features

- Calculation and parsing of basic operations and operators
- Fault-tolerant parsing of strings
- Support for complex and infinite numbers
- Propagation of uncertainty
- Interval arithmetic
- Support for all common number bases, including negative and non-integer radices, sexagesimal numbers, time format, and roman numerals
- Customizable implicit multiplication
- Matrices and vectors, and related operations
- Verbose error messages
- Arbitrary precision
- RPN mode
- Result display with customization options
- Exact or approximate calculations
- Symbolic calculation including factorization, simplification, differentiation, integration, and solving equations and inequalities
- Hundreds of flexible functions, including trigonometry, exponents and logarithms, combinatorics, geometry, calculus, statistics, finance, time and date, etc.
- Support for all SI units and prefixes, as well as imperial and other unit systems
- Automatic and explicit unit conversion
- Currency conversion with daily exchange rates
- Support for variables and constants, including physical constants and properties of chemical elements
- Import and export of CSV files
- Data sets with objects and associated properties in a database-like structure
- Plotting using Gnuplot with customization options
- Graphical user interfaces implemented using GTK or Qt, with flexible expression entry, calculation history, traditional calculator keypad, practical menus, and customizable meta modes
- Dialogs for management of functions, variables, and units
- Creation and editing of functions, variables, and units
- Easy editing of matrices and vectors
- Various tools for fast conversion between number bases, floating point conversion, calendar conversion, and percentage calculation
- Convenient interface to Gnuplot
- Configurable keyboard shortcuts
- Additional text-based interface with full functionality

## 2- Palm Calc

PalmCalc is a multipurpose application that includes a scientific calculator, unit converter, basic calculator, tip calculator, world clock, and BMI calculator.

### Features

- Scientific Calculator: Calculate math expressions with trigonometric functions, power and root functions, log functions, modulus function, nPr, and ncr. Specify angles in degrees or radians. Hyperbolic option available.
- Unit Converter: Perform multi-unit conversion in domains like temperature, length, weight, speed, volume, area, mass, and time. Use the wheel picker for easy conversion between units.
- Basic Calculator: Perform day-to-day calculations with expression calculation, calculation history, percentage calculation, and advanced memory operations.
- Tip Calculator: Calculate tips and split bills between multiple persons. Access standard tip percentages and support for all international currencies.
- World Clock: Keep track of time worldwide with analog and digital clock styles. Add different time zones and customize settings.
- BMI Calculator: Calculate BMI in English or Metric mode, with weight categorization and a wheel picker for easy selection.

### Platforms

## 3- CalculatorApp

CalculatorApp is an Android application that functions as a basic calculator, scientific calculator, and unit converter. It can be run on any Android mobile phone and developed using Android Studios.

## Calculator

The Windows Calculator app is a modern Windows app that offers standard, scientific, and programmer calculator functionality, as well as converters for units of measurement and currencies. It is regularly updated with new features and bug fixes, and can be obtained from the Microsoft Store.

### Features

- Standard Calculator functionality which offers basic operations and evaluates commands immediately as they are entered.
- Scientific Calculator functionality which offers expanded operations and evaluates commands using order of operations.
- Programmer Calculator functionality which offers common mathematical operations for developers including conversion between common bases.
- Date Calculation functionality which offers the difference between two dates, as well as the ability to add/subtract years, months and/or days to/from a given input date.
- Calculation history and memory capabilities.
- Conversion between many units of measurement.
- Currency conversion based on data retrieved from Bing.
- Infinite precision for basic arithmetic operations (addition, subtraction, multiplication, division) so that calculations never lose precision.

## 4- OpenCalc

OpenCalc is a lightweight calculator app for **Android** with a simple and beautiful design. It offers various themes, scientific mode, history, and supports both portrait and landscape orientation. The app is available on Google Play, F-Droid, and GitHub.

**5- Numi **

Numi is a calculator app for macOS that allows you to perform calculations by describing tasks naturally. It supports various features such as currency conversion, date calculations, and variables.

The CLI version of Numi also provides similar functionality, although some features like localization support and plugins/extensions are not yet implemented.

### Platforms

## 6- Insect

Insect is a free and open-source high-precision scientific calculator with full support for physical units. You can use the web version here.

## 7- Numbat

*Numbat* is a statically typed programming language for scientific computations with first class support for physical dimensions and units.

### Key Features

- Physical dimensions as types
- First-class physical units
- Comprehensive standard library
- Strict syntax
- Excellent error messages
- Interactive terminal
- Modular and customizable
- Assertions for correctness checks

## 8- Calculator (Android)

Calculator is a free and open-source simple but elegant Calculator app made with Flutter using Google’s Material Design with Currency (Exchange Rate) and Unit Converter.

## 9- Mint Calculator

Mint Calculator is a free simple calculator and unit converter app with Material Design 3 inspired by Windows Calculator.

### Features

- Standard Calculator
- Date Calculator
- Simple unit converter (Angle, Time, Data, Length, Area, Volume, etc…)

## 10- Multi-Calculator

Multi Calculagor is a free and open-source lightweight calculator for Android.

### Features

- Calculator: Perform basic arithmetic operations and advanced calculations, including power, square root, factorial, and percentage. Supports scientific calculations and input of scientific constants.
- Unit Converter: Convert between various units of length, area, volume, mass, temperature, and more.
- Date Calculator: Calculate date intervals and perform date calculations, such as finding future or past dates based on a specified date and number of days.
- Compass: Obtain information such as azimuth, magnetic declination, latitude and longitude, altitude, speed, magnetic field, address, and atmospheric pressure.
- BMI Calculator: Calculate BMI index based on height and weight, and provide corresponding health advice.
- Live Currency Exchange Rate Converter: Convert between multiple currency types based on real-time exchange rates.
- Uppercase Chinese Digit Converter: Convert Arabic numerals to uppercase Chinese numerals.
- Relative Salutation Calculator: Calculate Chinese titles based on kinship and determine the correct Chinese address.
- Financial Calculator: Calculate bank deposits, investment returns, loans, and VAT, with data visualization in charts.
- Random Number Function: Generate random numbers within a specified range.
- Equation Solving Function: Solve linear equations and quadratic equations in one variable.
- Shopping Assistant: Calculate discounts and unit prices quickly.
- Mathematical Statistics: Calculate various statistical measures, such as greatest common divisor, least common multiple, arithmetic mean, geometric mean, variance, standard deviation, and sum.

## 11- Engineering Calculator and Unit Converter

Engineering Calculator is a lightweight, yet handy math expression evaluation and unit conversion utility that is always at your fingertips.

## 12- CalcConv

CalcConv is a Command-Line Calculator with additional functionalities. This project was developed as part of my mini project for Object Oriented Programming Using C++.

It includes 4 modules: Basic Module, Quadratic Equation Solver, Unit Converter and Logging.

## 13- Qubit

This is an open-source handy calculator, based on Rust and WebAssembly.

It also includes a unit conversion:

- Angle
- Area
- Digital Information
- Length
- Mass
- Speed
- Time
- Temperature

## 14- Kalker

Kalker (or “kalk”) is a calculator program/website that supports user-defined variables, functions, differentiation, and integration. It runs on Windows, macOS, Linux, Android, and in web browsers (with WebAssembly).

### Features

- Operators:
`+`

,`-`

,`*`

,`/`

,`!`

- Groups:
`()`

,`[]`

,`⌈ceil⌉`

,`⌊floor⌋`

- Vectors: (x, y, z, …)
- Matrices: [x, y, z; a, b, c; …]
- Pre-defined functions and constants
- User-defined functions and variables.
`f(x, y) = xy`

,`x = 5`

- Root finding using Newton’s method (eg. x^2 = 64). Note: estimation and limited to one root
- Derivative of functions (derivatives of noisy functions or of higher order can be a bit inaccurate).
`f'(2)`

,`sin'(-pi)`

- Integration.
`∫(0, pi, sin(x) dx)`

or`∫(0, π, sin(x) dx)`

, maybe sometimes be slightly off - Understands fairly ambiguous syntax. Eg.
`2sin50 + 2xy`

- Syntax highlighting
- Special-symbol completion on tab. Eg. write
`sqrt`

and press tab. It will be turned into`√`

- Sum function:
`sum(start, to, expression)`

Eg.`sum(1, 3, 2n+1)`

is the same as`2*1+1 + 2*2+1 + 2*3+1`

=`15`

- Piecewise functions:
`f(x) = { f(x + 1) if x <= 1; x otherwise }`

, pressing enter before typing the final`}`

will make a new line without submitting - Load a file including predefined functions and constants. For example, if you’re going to use kalker for physics, you load up your file with physics functions/constants when starting kalker. This is done either using the
`-i file`

flag or by putting files in a certain directory and then doing`load filename`

inside kalker. More about files here - Different number bases: Either with a format like
`0b1101`

,`0o5.3`

,`0xff`

or a format like`1101_2`

. The latter does not support letters, as they would be interpreted as variables - Misc: separate expressions by a semicolon to write them on the same line, use the
`ans`

variable to get the value of the previously calculated expression

### Platforms

- macOS
- Arch Linux
- Ubuntu
- Nix/ NixOS
- NetBSD

## 15- Calculator N+

Calculator N+ is a powerful Android calculator that utilizes the Symja library and displays results in Latex. It is an open-source project that provides an ad-free application for studying purposes. A lite version is available on the Google Play Store.

## 16- Calcway

Calcway is a free and open-source simple calculator application built with React.

### Features

- Responsive design
- User-friendly interface
- Customization themes
- Keyboard support
- Basic calculations

## 17- Calculator

The calculator is the essential tool for your smartphone, simple and easy to use with a sleek design – the perfect calculator for Android.