A mortgage rule of thumb

On a 30-year mortgage, take the interest rate, add one (1) to it, and multiply by the loan amount. You get roughly the total you will pay on your mortgage each year. The full skinny, normalized against a $100,000 mortgage:

Interest rate	Monthly Payment	Annual Payment	Ratio
4.00%	$477.42	$5,728.98	0.06
5.00%	$536.82	$6,441.86	0.06
6.00%	$599.55	$7,194.61	0.07
7.00%	$665.30	$7,983.63	0.08
8.00%	$733.76	$8,805.17	0.09
9.00%	$804.62	$9,655.47	0.10
10.00%	$877.57	$10,530.86	0.11

Divide by 12 to get the monthly, obviously.