How long to roas a turkey

[CeciC]

I feel very stupid with this question, but I have never roast a turkey, so how long (more or less) to roast a 6kg turkey. Someone told me that is 1 hour per 1/2 kg, that can't be true can it be?
I don't want to food poisoned my ILs even thought it would be a good excuse for not doing Christmas dinner again
Thanks

according to the food standards agency calculator it will take 4 hours at 180 degrees

it gives this info:

As a general guide, in an oven preheated to 180ºC (350ºF, Gas Mark 4):

?for a turkey under 4.5kg, allow 45 minutes per kg plus 20 minutes

?for a turkey weighing between 4.5kg and 6.5kg, allow 40 minutes per kg

?for a turkey over 6.5kg, allow 35 minutes per kg

Tip: Cover your turkey with foil during cooking and uncover for the last 30 minutes to brown the skin. To stop the meat drying out, baste it every hour during cooking