Numi is a handy calculator app for macOS. It allows you to describe tasks naturally and instantly get an accurate answer. For example, $20 in euro - 5% discount or today + 2 weeks.
You can use Numi from command line on Linux and macOS. The CLI version is still experimental, and not all features are supported. The recommended way is to install using Homebrew:
brew install nikolaeu/numi/numi-cli
You can also download the most recent CLI version manually from the releases page. New Alfred workflow for CLI can be downloaded from the releases page as well. Note, there's no need to enable Alfred integration in app preferences with the new workflow.
Usage example: numi-cli "20 inches in cm". Pass -h for more options.