Accuracy of steps to calories taken from Iphone 5s

njw97

So I have walked 7,200 steps thus far today, which has equated to 2.7 miles on my Iphone. According to every source I've read this should have burned at least over 200 calories, but in myfitnesspal it says I've burned 129. I'm a 6ft male weighing 180 pounds. Can anyone give advice on whether MFP is accurate when converting these steps to calories or am I better just converting each mile into 100 calories?