Google Calculator

Google calculator is a hidden feature of Google search. No need of separate URL. Just log in to Google.com and type in whatever you want to calculate. You can type anything like 100+130 or it can even be trigonometry of sin(30) or it can be anything. Operators that can be used are

Operator	Function	Example
+	addition	5+3
-	subtraction	9-4
*	multiplication	8*5
/	division	23/2
^	exponentiation(raise to the power of)	6^4
%	modulo	8%7
choose	X choose Y determines the number of ways of choosing a set of Y elements from a set of X elements	19 choose 3
th root of	calculates the nth root of a number	6th root of 64
% of	X % of Y computes X percent of Y	20% if 150
sqrt	square root	sqrt(25)
sin, cos etc...	Trigonometric function	tan(45)
ln	logarithm to the base e	ln(4)
log	logarithm to the base 10	log(pi)
!	Factorial	8!

 

It also understand the value of 'pi'. Like, you can use sin(pi/3). You can also use parenthesis to make a perfect equation. The equation inside the parenthesis will be evaluated first and then the rest.
You can also use this as converters. If you want to know x kms in terms of miles, then just type in 10kms in miles.
Conversion from decimal to binary is easy. For example, type 54 to binary. You can use hexadecimal, octal and binary numbers. Prefix hexadecimal numbers with 0x, octal numbers with 0o and binary numbers with 0b. For example: 0x7f + 0b10010101.
It also understands when you say speed of light or just c. 
Not all the features of Google Calculator are included here. You can convert decimal to hexadecimal or even roman numerals. Just as described above with binary conversion. Google Calculator also understands some complex statements like this G*(6e24 kg)/(4000 miles)^2. It understands these 'kg', 'miles' and even the constants like 'G'.

Not all the features of Google Calculator is described here. Just get on Google and start experimenting with this. 
Isn't this cool? A search engine not just a search engine.