For openSUSE Tumbleweed run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:drankinatty/openSUSE_Tumbleweed/home:drankinatty.repo
zypper refresh
zypper install galculator
For openSUSE Leap 42.3 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:drankinatty/openSUSE_Leap_42.3/home:drankinatty.repo
zypper refresh
zypper install galculator
For openSUSE Leap 42.2 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:drankinatty/openSUSE_Leap_42.2/home:drankinatty.repo
zypper refresh
zypper install galculator
For openSUSE Leap 15.1 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:drankinatty/openSUSE_Leap_15.1/home:drankinatty.repo
zypper refresh
zypper install galculator