# What is the CSS calc() function and how is it used?Richard Wconst t="undefined"!=typeof HTMLImageElement&&"loading"in HTMLImageElement.prototype;if(t){const t=document.querySelectorAll("img[data-main-image]");for(let e of t){e.dataset.src&&(e.setAttribute("src",e.dataset.src),e.removeAttribute("data-src")),e.dataset.srcset&&(e.setAttribute("srcset",e.dataset.srcset),e.removeAttribute("data-srcset"));const t=e.parentNode.querySelectorAll("source[data-srcset]");for(let e of t)e.setAttribute("srcset",e.dataset.srcset),e.removeAttribute("data-srcset");e.complete&&(e.style.opacity=1,e.parentNode.parentNode.querySelector("[data-placeholder-image]").style.opacity=0)}}

The CSScalc() function is a powerful tool that allows you to perform calculations within CSS property values. It provides a way to dynamically compute values based on mathematical expressions, enabling more flexible and responsive designs. Thecalc() function can be used with various CSS properties that accept numeric values, such as width, height, margin, padding, and more. Thecalc() function takes a mathematical expression as its argument, which can include addition (+), subtraction (-), multiplication (*), and division (/) operations. It allows you to combine different units of measurement, such as pixels (px), percentages (%), viewport units (vw, vh), and more, within the same expression. Here's an example to illustrate how thecalc() function works:

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v {
width: calc(100% - 20px);
height: calc(50vh + 10px);