In the past decades of spreadsheet calculations being dominated by Microsoft Excel, then a few years ago Google came up with a very powerful alternative to work with spreadsheets online: its very own Google Sheets as part of their business online applications.
Google promotes it with: "Google Sheets is available on all your devices and has all the features you come to expect from spreadsheet software. Sheets also allows you to collaborate with others in real time."... and it is a fair promise.
You can see REALTIME, who is working on what.
It is a very nice way to demonstrate you calculations with partners and the team. It comes with an API and the professional package for Google Apps at work is currently $5 per month per user.