Generally I don't get asked for an estimate until after I've done the design, so these numbers are code, unit test and very basic test on real hardware only. These are the rules I use:
- If I think I understand everything it involves, then I take my estimate for all the bits, add them up and multiply by 4.
- If I think I understand everything it involves, have done something similar before, and gone through my list of things to do a couple of times looking for stuff I've forgotten, I can multiply it by 2 instead. If I'm unsure how long something will take I am never allowed to round down.
- If I find myself sizing something with the word 'just' in the sentence, I'm missing something big. (e.g. Then it's just a matter of recreating the error condition and making sure my error gets triggered correctly.)
- If I'm not almost finished (i.e. functionality working with some hacks, unit test passes) by halfway through the time then I'm going to miss my deadline.
- I am still mystified as to where that other half of the time goes (I have a proper 90% rule going on), but some of it is getting my code in a shape where I'm happy about checking it in - dealing with comments so they mean things to people other than me, removing ugly bits of code, checking with co-workers in places where I wasn't sure I'd made the right decision. My maximum speed on this is about 500 lines a day. Some more time is then spent getting things back working again, because I'll have broken things in the process. And I need at least a day to get a sandbox build behaving properly, and willing to run on my hardware.
- If I think I understand everything it involves, then I take my estimate for all the bits, add them up and multiply by 4.
- If I think I understand everything it involves, have done something similar before, and gone through my list of things to do a couple of times looking for stuff I've forgotten, I can multiply it by 2 instead. If I'm unsure how long something will take I am never allowed to round down.
- If I find myself sizing something with the word 'just' in the sentence, I'm missing something big. (e.g. Then it's just a matter of recreating the error condition and making sure my error gets triggered correctly.)
- If I'm not almost finished (i.e. functionality working with some hacks, unit test passes) by halfway through the time then I'm going to miss my deadline.
- I am still mystified as to where that other half of the time goes (I have a proper 90% rule going on), but some of it is getting my code in a shape where I'm happy about checking it in - dealing with comments so they mean things to people other than me, removing ugly bits of code, checking with co-workers in places where I wasn't sure I'd made the right decision. My maximum speed on this is about 500 lines a day. Some more time is then spent getting things back working again, because I'll have broken things in the process. And I need at least a day to get a sandbox build behaving properly, and willing to run on my hardware.
edit: formatting