Converting Spreadsheets to online Calculator

I have a client who has some pretty advanced spreadsheets with some fairly complex formulas. They’d like to embed these in their site and I’ve been able to do so with Microsoft Office Online but it’s really horrible looking. I’m curious if there are any wordpress plugins or online services that will convert a spreadsheet to a form or advanced calculator. I’ve looked into a few spreadsheet plugins but they don’t have the advanced formulas needed.

Thanks all!