calc()The calc() CSS function computes mathematical expressions such a calc(100%/3 - 1em).cssCSSwidely2015-07-292018-01-29https://drafts.csswg.org/css-values-3/#calc-notationcalchttps://developer.mozilla.org/docs/Web/CSS/Reference/Values/calccss.types.calccss.types.calc.gradient_color_stopscss.types.calc.nestedcss.types.calc.number_valueshttps://nowyoucanuse.com/features--calc.html