{"id":4016,"date":"2016-03-12T12:50:43","date_gmt":"2016-03-12T14:50:43","guid":{"rendered":"https:\/\/www.kadunew.com\/blog\/?p=4016"},"modified":"2016-03-12T12:50:43","modified_gmt":"2016-03-12T14:50:43","slug":"css-com-box-sizing-border-box","status":"publish","type":"post","link":"https:\/\/www.kadunew.com\/blog\/css\/css-com-box-sizing-border-box","title":{"rendered":"CSS com box-sizing: border-box"},"content":{"rendered":"<p>Por padr\u00e3o as propriedades <em>width<\/em> e <em>height<\/em> n\u00e3o definem o tamanho final dos elementos HTML. Isso porque o tamanho final do elemento vai ser calculado com a soma das propriedades <em>width<\/em>, <em>padding<\/em> e <em>border<\/em>, por exemplo.<\/p>\n<p><!--more--><\/p>\n<p>Considerando um elemento onde voc\u00ea aplique as seguintes propriedades:<\/p>\n<ul>\n<li>Largura (width) de 50%;<\/li>\n<li>Padding (right e left) de 5%;<\/li>\n<li>Border (right e left) de 1%;<\/li>\n<li>Voc\u00ea ter\u00e1 no final um elemento com <strong>62% de largura<\/strong>.<\/li>\n<\/ul>\n<p>Esse \u00e9 comportamento padr\u00e3o Box model, ou seja, as <strong>propriedades se relacionam<\/strong> para determinar o tamanho final do elemento.<\/p>\n<h2>Vantagem do  box-sizing<\/h2>\n<p>Existe no CSS a propriedade <em>Box-sizing<\/em> com o valor <em>border-box<\/em> que altera a forma de como o <strong>Box Model \u00e9 calculado<\/strong>, assim o <em>padding<\/em> e <em>border<\/em> s\u00e3o incorporados \u00e0 largura do elemento. Dessa forma garantimos que o elemento ter\u00e1 uma largura de 50%.<\/p>\n<p>Essa propriedade CSS <strong>facilita as contas<\/strong> e deixa os n\u00fameros mais claros, assim voc\u00ea n\u00e3o precisa ficar calculando o tamanho total do elemento.<\/p>\n<p>Considerando que voc\u00ea deseja posicionar dois elementos <em>divs<\/em> <strong>um ao lado do outro<\/strong> com  um espa\u00e7amento interno (padding) de 5%, e que a soma dos dois ocupem toda a largura da p\u00e1gina:<\/p>\n<p>Seu CSS ficaria assim:<\/p>\n<pre class=\"brush: css; title: CSS; notranslate\" title=\"CSS\">\r\ndiv {\r\n  float: left;\r\n  width: 50%;\r\n  padding:5%;\r\n}\r\n<\/pre>\n<p>Para sua surpresa o layout quebra, pois a largura total das <em>divs<\/em> ser\u00e1 de 60% . Essa quest\u00e3o \u00e9 resolvida usando o <strong>box-sizing: border-box<\/strong>. Ela garante que a largura ser\u00e1 de 50%.<\/p>\n<p>Use box-sizing em todos os seus projetos. Aplique o <strong>seletor universal<\/strong>, assim:<\/p>\n<pre class=\"brush: css; title: CSS; notranslate\" title=\"CSS\">\r\n* {\r\n    -webkit-box-sizing: border-box;\r\n       -moz-box-sizing: border-box;\r\n            box-sizing: border-box;\r\n}\r\n<\/pre>\n<div class=\"obs\">\nPor\u00e9m, n\u00e3o esque\u00e7a: aplicar box-sizing em um projeto j\u00e1 pronto certamente ir\u00e1 quebrar seu layout. Sendo assim voc\u00ea ter\u00e1 que recalcular as medidas dos elementos novamente.\n<\/div>\n<h2>Suporte nos navegadores<\/h2>\n<p>Internet Explorer tem suporte at\u00e9 a vers\u00e3o do IE8. Em um caso muito raro voc\u00ea precisar tem um <a href=\"https:\/\/github.com\/Schepp\/box-sizing-polyfill\">polyfill para box-sizing<\/a> pra IE6 e IE7.<\/p>\n<p>Confira o suprote a todos navegadores no link: <a href=\"http:\/\/caniuse.com\/#feat=css3-boxsizing\">http:\/\/caniuse.com\/#feat=css3-boxsizing<\/a><\/p>\n<p>Curta a p\u00e1gina do <a href=\"https:\/\/www.facebook.com\/pages\/Kadunew-Artigos-e-tutoriais-sobre-Web-Design\/787883281258323\" title=\"Artigos e tutoriais sobre Web Design\" target=\"_blank\">blog kadunew<\/a> no Facebook. Siga-me no Twitter: <a href=\"http:\/\/twitter.com\/kadunew\" rel=\"nofollow\">@kadunew<\/a>.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Por padr\u00e3o as propriedades width e height n\u00e3o definem o tamanho final dos elementos HTML. Isso porque o tamanho final do elemento vai ser calculado com a soma das propriedades width, padding e border, por exemplo.<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[4],"tags":[],"class_list":["post-4016","post","type-post","status-publish","format-standard","hentry","category-css"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v23.6 - https:\/\/yoast.com\/wordpress\/plugins\/seo\/ -->\n<title>CSS com box-sizing: border-box<\/title>\n<meta name=\"description\" content=\"Utilize box-sizing: border-box no seu CSS e facilite o c\u00e1lculo de largura e altura dos seus elementos.\" \/>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/www.kadunew.com\/blog\/css\/css-com-box-sizing-border-box\" \/>\n<meta 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