To accurately measure items on your screen you can use the free utility, Pixel Ruler. I've found this helpful when I have to upload a picture that's a specific measurement, such as a blog banner, or profile photo.

要准确测量屏幕上的项目，可以使用免费的工具Pixel Ruler。 当我必须上传特定尺寸的图片(例如博客横幅或个人资料照片)时，这对我很有帮助。

You can drag the ruler to any position on the screen, to line up the zero mark with the left edge of the object that you want to measure.

您可以将标尺拖动到屏幕上的任何位置，以使零标记与要测量的对象的左边缘对齐。

Then, point to the ruler where it lines up with the right edge of the object, to see the width in pixels. In the screen shot above, the rectangle is 223 pixels wide.

然后，指向标尺与对象右边缘对齐的位置，以查看像素宽度。 在上面的屏幕截图中，矩形的宽度为223个像素。

The ruler has three control buttons at its top left -- an arrow, a triangle and a line:

标尺的左上方有三个控制按钮-箭头，三角形和一条线：

• To measure the height, rotate the ruler to vertical, by clicking the arrow button.要测量高度，请通过单击箭头按钮将标尺旋转到垂直方向。
• Click the triangle button to change the ruler colour, or to access the Pixel Ruler web site单击三角形按钮更改标尺颜色，或访问Pixel Ruler网站
• To close the ruler, click the line button.要关闭标尺，请单击行按钮。