Calculator applications

Generic calculators

Integrated calculators

Calculators integrated to their respective Desktop environments.

gnome-extra/gnome-calculator https://wiki.gnome.org/Apps/Calculator
A calculator application for GNOME

kde-apps/kcalc https://www.kde.org/applications/utilities/kcalc https://utils.kde.org/projects/kcalc
KDE calculator

mate-extra/mate-calc http://mate-desktop.org
A calculator application for MATE

x11-apps/xcalc http://xorg.freedesktop.org/
scientific calculator for X

x11-plugins/wmcalc http://dockapps.windowmaker.org/file.php/id/130
A WindowMaker DockApp calculator

Scientific calculators

sci-calculators/qalculate-gtk https://qalculate.github.io/
Modern multi-purpose calculator

sci-calculators/calcoo http://calcoo.sourceforge.net/
Scientific calculator designed to provide maximum usability

sci-calculators/wcalc http://w-calc.sourceforge.net/
A flexible command-line scientific calculator

dev-perl/Math-Calc-Units http://search.cpan.org/dist/Math-Calc-Units/
Human-readable unit-aware calculator

Calculator plugins

app-vim/vimcalc http://www.vim.org/scripts/script.php?script_id=3329
vim plugin: provides an interactive calculator inside vim

app-xemacs/calc http://xemacs.org/
Emacs calculator

sci-calculators/calculator http://www.fox-toolkit.org/
Scientific calculator based on the FOX Toolkit

Tecnical calculators

IP calculators

dev-python/ipcalc https://pypi.python.org/pypi/ipcalc/
IP subnet calculator

net-misc/ipcalc http://jodies.de/ipcalc
IP Calculator prints broadcast/network/etc for an IP address and netmask

net-misc/ipv6calc http://www.deepspace6.net/projects/ipv6calc.html
IPv6 address calculator

net-misc/sipcalc http://www.routemeister.net/projects/sipcalc/
Sipcalc is an advanced console-based IP subnet calculator

HEX calculators

sci-calculators/hcalc http://www.delorie.com/store/hcalc/
DJ's Hex Calculator

sci-calculators/hexcalc ftp://ftp.x.org/R5contrib/
A simple hex calculator for X

Calendar calculators

dev-perl/Date-Calc http://search.cpan.org/dist/Date-Calc/
Gregorian calendar date calculations

dev-perl/Date-Pcalc http://search.cpan.org/dist/Date-Pcalc/
Gregorian calendar date calculations

x11-plugins/wmCalClock http://dockapps.windowmaker.org/file.php/id/9
WMaker DockApp: A Calendar clock with antialiased text

Other

dev-perl/Color-Calc http://search.cpan.org/dist/Color-Calc/
Simple calculations with RGB colors

media-plugins/vdr-calc http://www.vdrcalc.bmschneider.de/index2.html
VDR Plugin: OSD Calculator

sci-calculators/keurocalc http://opensource.bureau-cornavin.com/keurocalc/index.html
A universal currency converter and calculator

sci-calculators/pcalc https://github.com/vapier/pcalc
the programmers calculator

sci-calculators/transcalc http://transcalc.sourceforge.net
Microwave and RF transmission line calculator

sci-libs/libticalcs2 http://lpg.ticalc.org/prj_tilp/
Library for communication with TI calculators

sci-mathematics/calc http://www.isthe.com/chongo/tech/comp/calc/
An arbitrary precision C-like arithmetic system

sys-auth/otpcalc http://killa.net/infosec/otpCalc/
A One Time Password and S/Key calculator for X