This Really Needs and XKCD cartoon.

Time to assemble IKEA furniture =

X/N

Where N = The number of pieces you have done to that point (1st piece, n=1. second, n=2, etc.

Where X is the base time calculated as follows:

X = B + (L*.5)*5) + (S*.1)* 10) + (E*15) + (G*20) - (P*10) + (I*15)

Where B = Base time dependent on furniture size: Small=15 min, Medium = 30min, Large = 60 Minutes

Where L = Number of larger pieces in the unit, the .5 conversion is the number that will be mistake for other pieces and put in place until the builder realized that they don't go there. The '5' equals 5 minutes per such error.

Where S = Number of small pieces, also mistaken for each other (multiple screws resembling each other, that roll away or fall down the stairs) .1 is the conversion rate for these mistakes. The '10' is the time wasted unscrewing or undrilling said pieces.

Where E = Errors made that can be fixed, such as using a part on the front that is supposed to be on the back. The 15 is the amount of time used working backwards to undo the mistake.

Where G = Giant error that cannot be undone. Such as putting a part on the front that gets sealed in by other pieces or is put in upside down since you were assembling the furniture upside-down. 20 minutes per major mistake will be used trying to see if the error can be fixed or cursing loudly.

Where P = Extra people helping out. P may have a value of no more than 2. After that its just too many damn cooks.

Where I = Interruptions. The phone rings, or someone arrives at the door. 15 minutes per incident while you balance a huge piece of glass while picking up the phone or bracing things so you can answer the door. Much of the 15 minutes per incident will be trying to figure out where you were on the instructions. Interruptions will not happen at good times to take a break.