If you want multiple lines consider this:
<textarea rows="2"></textarea>
Specify rows as needed.
Increasing the font size on a text box will usually expand its size automatically.
<input type="text" style="font-size:16pt;">
If you want to set a height that is not proportional to the font size, I would recommend using something like the following. This prevents browsers like IE from rendering the text inside at the top rather than vertically centered.
.form-text{
padding:15px 0;
}
Note that if you want a multi line text box you have to use a <textarea> instead of an <input type="text">.
Use CSS:
<html>
<head>
<style>
.Large
{
font-size: 16pt;
height: 50px;
}
</style>
<body>
<input type="text" class="Large">
</body>
</html>
<input type="text" style="font-size:xxpt;height:xxpx">
Just replace "xx" with whatever values you wish.
With inline style:
<input type="text" style="font-size: 18pt; height: 40px; width:280px; ">
or with apart CSS:
HTML:
<input type="text" id="txtbox">
CSS:
#txtbox {
font-size: 18pt;
height: 42px;
width : 300px;
}
Source: Stackoverflow.com