Providing an estimate isnt impossibly hard, I've found there is much more forgiveness for putting a long estimate in, and then coming in early, than putting a short one in, and coming in late.
Stuff I've not done before can be a real challenge, I just add a 50% slop factor, but I won't even give a guess until I can at least have a modicum of understanding of the complexity of the problem, technologies and people involved.
Generally for stuff I'm familiar with - I take how long I think its going to take, then double it, and thats what I give to my management. For stuff I'm not familiar with, I guess based on like-like work, and then add 30-50% more time in, then double that. For some of our customers however, working with them incurs a time penalty, so I add another 20-40% on top to their estimates.
The feedback I've been given is that my time scopings are reasonably accurate however. So while I feel silly turning in an estimate for 24 hours for a task that I think ought to take 8, time and time again, it takes closer to 18-20 hours rather than the 8 I feel it ought to (usually because of external factors outside of my control).
Stuff I've not done before can be a real challenge, I just add a 50% slop factor, but I won't even give a guess until I can at least have a modicum of understanding of the complexity of the problem, technologies and people involved.
Generally for stuff I'm familiar with - I take how long I think its going to take, then double it, and thats what I give to my management. For stuff I'm not familiar with, I guess based on like-like work, and then add 30-50% more time in, then double that. For some of our customers however, working with them incurs a time penalty, so I add another 20-40% on top to their estimates.
The feedback I've been given is that my time scopings are reasonably accurate however. So while I feel silly turning in an estimate for 24 hours for a task that I think ought to take 8, time and time again, it takes closer to 18-20 hours rather than the 8 I feel it ought to (usually because of external factors outside of my control).