Whole chicken roasting time

The shops are likely going out of their way not to get sued by sticking to safety guidelines rigidly. The packet instructions usually result in a dry and overcooked bird. The various other times and temperatures are all attempts to get a safely cooked, attractively browned bird without overcooking.

However, roasting meat based on oven temperature and the weight of the joint is the wrong way to go about things, because ovens are rarely calibrated correctly (the temperature is often wildly at variance to that set on the dial) and the weight of the meat is rarely nicely rounded.

If you really want to cook any meat (and many other foods) properly, you'll invest in a digital probe thermometer. Then you can simply cook the meat until it reaches a safe internal temperature and no more. They aren't expensive, you can get them from Amazon, and once you've got one you won't know how you did without it.

I believe the shop is being overly cautious as all manufacturers are. They have to cover themselves from being seued. In pretty much every case I've ever seen the cooking temperatures are overstated to the point the meat is pretty much inedible. Pork packages say to cook to 165 which in culinary terms is " dead pork ". Aaronut has a good point about using a thermometer as cooking times can vary from oven to oven. A little test you can do if you don't have a thermometer is check the firmness of the breast meat. If you've done it enough you can easily tell this way.