If you need a true free alternative, is your answer. Google commissioned this font specifically to be a metric-compatible substitute for Calibri. This means:
Everett was a minimalist in a maximalist world. While his colleagues obsessed over flashy, jagged display fonts that screamed for attention, Everett sought the quiet efficiency of
Calibri is a humanist sans-serif typeface family designed by the renowned Dutch type designer Lucas de Groot. It was released to the public in 2007 alongside Microsoft Windows Vista and Microsoft Office 2007. At the time, it replaced the stalwart Times New Roman as the default font in Microsoft Word, marking a significant shift in default document aesthetics from classic serifs to modern sans-serifs.