OK.... I actually worked harder than that. But this was the incline % that I used for my entire workout tonight. I started off walking uphill for a 1/2 hour at 3.5 mph. Then increased the speed to 4.5 and ran slowly for 15 minutes. And then finished things up with 15 minutes of walking. When I was done it said I burned 900 calories! Not sure how accurate the treadmill calculator is though.
The hardest part was trying to continue running at a 15% grade during the middle part of my workout after already walking uphill for 30 minutes. Then I just tried to hang on at the end while rocking out to Daft Punk's "One More Time". This is a good mantra to repeat to yourself, especially while on the boring treadmill. Plus, the beat is a perfect fast walking pace and I was able to step to it for the last 15 minutes.