If you really need very quick estimation, you can do work breakdown structure with every task for 1-2 days or smaller and after this estimate every task by providing min and max estimated values.
sum of min and max values specify interval for the whole task. This gives information abouts risks to your boss, which is always very useful.
You will obtain some interval, e.g. 12-15 day or 5-30 days - this is much more useful than 16 day instead of mentioned intervals.
It can be useful for you good book by Steve McConnel Software Estimation: Demystifying the Black Art.
