Figuring out savings percentages

Here's an example thanks Chapx!:
You have spent $270.77 and saved $1136.14, which when added ($1406.91) give your YDT total before any savings. To get your savings percentage divide savings by YTD total before savings and multiply times 100%:
$1136.14 / $1406.91 = 0.8075 x 100% = 80.75% savings