How long will it take?

Estimating how long a task takes, for instance in programming, is always difficult.

Here is a bookmarklet that you can use. Create a bookmark with this as the url

javascript:var units = prompt("What is the unit (days, months, hours, coffees)?");var t1 = parseFloat(prompt("How long it will take, if everything goes right?"));var t2 = parseFloat(prompt("How long will it take, knowing how some things usually go wrong?"));var t3 = parseFloat(prompt("How long will it take if everything goes wrong, and there are lots of unforeseen issues - you are 99% sure you can get it done within this amount of time"));alert("It will take " + Math.round(((t1+(4.0*t2) + t3)/6.0)*10)/10 + " " + units);

The algorithm used is this:

t1 = how long it takes if everything goes as planned.
t2 = how long it takes if there are some problems along the way
t3 = how long it takes if everything goes wrong (this is the time that you are 99% sure it takes to finish it even if everything goes wrong)

(t1+(4*t2) + t3) / 6