GNOME Calculator – How to Run Multiple Instances Simultaneously

The tiny script below will do what you want. You need to install wmctrl for it to work:

sudo apt-get install wmctrl

After you've installed wmctrl, paste the text below into a file and call it whatever you want. I called mine calc-activate.sh.

#!/bin/bash
#This script switches focus to gnome-calculator if it is running.
#If it is not running, it will run gnome-calculator.

if [ "$(wmctrl -l | grep Calculator)" != "" ]; then
    wmctrl -a "Calculator"
else
    gnome-calculator &
fi

After saving, the text file, make it executable either by right clicking and going to the permissions tab and checking off the Execute boxes, or do it from the terminal with the chmod command).

Now you can set your multimedia keys:

• For Ubuntu 11.10 and earlier, go to: System → Preferences → Keyboard Shortcuts
• For 12.04 and later, hit the Super key, type "shortcut" then hit Enter.
• Now find the "Launch calculator" shortcut, click on it and hit backspace to disable it.
• Now you can add a new custom shortcut. Point the command to the full path of the script you just saved. Click on the new command and press the calculator button to assign it. Voila!

Please note: Since wmctrl looks for a program titled "Calculator" the above script snippet might not work with other languages. To fix, change Calculator so it matches the window title of gnome-calculator.

Danish example:

if [ "$(wmctrl -l | grep Lommeregner)" != "" ]; then
    wmctrl -a "Lommeregner"
else
    gnome-calculator &
fi

The pre-installed (GNOME) Calculator application on Ubuntu 18.04 is a snap application, it doesn't have .desktop launcher(s) for the application at traditional place(s), e.g. /usr/share/applications/. Check the /var/lib/snapd/desktop/applications/ directory instead.

Alternatively, you may consider creating a custom .desktop launcher for the application by hand. To do so, follow the steps below.

1. Create a new file, say calculator.desktop in your ~/.local/share/applications/ directory. You can do that by running the following in Terminal

   touch ~/.local/share/applications/calculator.desktop
   

2. Open this file with a text-editor, for example by running

   gedit ~/.local/share/applications/calculator.desktop
   

3. Add the following lines to this file and save the file.

   [Desktop Entry]
   Name=Calculator
   Comment=Perform arithmetic, scientific or financial calculations
   Exec=/snap/bin/gnome-calculator
   Type=Application
   Icon=accessories-calculator
   Terminal=false
   NoDisplay=false
   

You may also remove the snap version by running

snap remove gnome-calculator

and install the traditional apt versions by running

sudo apt install gnome-calculator