If you need to calculate some figures, while surfing on the internet ,then no need to open calculator in window or to take any search engine . You can do simple calculation easily in the browser itself. It is done by simple java script, which is described below. You just need to write that script in address bar and press enter and the answer would display immediately in an dialog box.
Answer will be displayed in dialog box as shown below.
You can use +, -, *, /, % and can perform calculation easily without open windows calculator.