Many people are really bad at estimating how much time a task will take. Perhaps you estimate you’ll need about an hour, and it really takes you 3-4 hours to finish. Or maybe you allocate 30 minutes for a task, and you’re done in 5 minutes. What can you do to get better at making accurate estimates?
Here are several techniques you can use to make better time estimates:
Calculate Your Fudge Ratio
The best place to start is to measure your current estimation accuracy.
Make a to-do list of upcoming tasks to complete, and jot down an off-the-cuff estimate for how long you expect each task to take. As you complete each task, record the time you actually spend on each one. Then add up your total time spent, and divide it by your total time estimate for the collection of tasks. That’s your fudge ratio.
For example, if you estimate that a certain list of tasks will take 12 hours to complete, but they really take 15 hours, then your fudge ratio is 15/12 = 1.25. This means you it took you 25% longer than expected to complete the tasks.
If you measure your fudge ratio for a variety of tasks, you’ll probably find that for individual tasks, your fudge ratio varies tremendously, perhaps ranging as widely as 0.1 to 10.0. However, for groups of tasks that collectively require a few days to complete, you may notice that your fudge ratio settles into a fairly narrow range. When you average enough tasks, your fudge ratio converges on a consistent figure.
My average fudge ratio is about 1.5. This means that whenever I make an off-the-cuff estimate for how long a task will take, on average I’m too optimistic; the task ends up taking about 50% longer than my initial guess. For any particular individual task, my estimates may be much more inaccurate. However, if I estimate that a collection of tasks will require about 2 days to complete, it’s a safe bet they’ll really require about 3 days.
Once you know your fudge ratio, you can use it to generate more accurate estimates for groups of tasks. Just add up your off-the-cuff estimates, and multiple the total by your known fudge ratio. This will tend to be a fairly accurate estimate.
I tend to be consistently optimistic when estimating the time required for certain tasks. Knowing my fudge ratio has NOT made my initial estimates more accurate. My off-the-cuff estimates are just as inaccurate as they’ve always been. However, when I multiple my estimates by the fudge ratio, the estimates come pretty close to the time required. This helps me budget my time better.
Based on my fudge ratio, I know that if I want to complete about 8 hours of actual work in a day, I should only list about 5 hours and 20 minutes worth of tasks based on my off-the-cuff time estimates (5:20 = 8 hours / 1.5). While it might seem silly to make this kind of compensation every day, in practice it works quite well — far better than the alternative of listing 8 hours of tasks and then either pushing myself to work a 12-hour day or feeling bad that I only completely 2/3 of my tasks. Self-sabotage can make things even worse when I subconsciously know I’m trying to do the impossible.
It’s better to make a reasonable task list that I can actually complete by the end of the day instead of beating myself up for being bad at estimating. Even if my daily task list seems too short at first glance, it feels good to cross off the final task at the end of the day. Due to daily variations, this isn’t perfectly accurate, but overall it’s better than anything else I’ve tried, and it encourages a sustainable daily rhythm without overworking or under-working.
I recommend using at least 10-20 hours of tasks for your initial fudge ratio calculation. If you based your calculation on only a few hours of tasks, your fudge ratio may not be accurate enough.
Of course it’s a good idea to recalculate your fudge ratio every once in a while. Once a quarter should be fine. It’s also wise to update it whenever the nature of your work changes, such as when you begin a new project or switch companies or careers.
If you want to get a little more detailed, you can calculate different fudge ratios for different kinds of work. Personally I don’t do this, but if you think it’s likely that different tasks will yield significantly different fudge ratios, it may be a good idea. For example, if you’re a student who finds that math homework has a fudge ratio of 0.9, but term papers have a fudge ratio of 1.7, you’ll probably want to maintain separate fudge ratios to create better estimates.
If you manage a team of people, you can calculate a fudge ratio for each member of your team (with or without their knowledge). Ask for time estimates from each team member for a collection of tasks, measure the actual time required, and calculate the fudge ratio for each team member. Whenever you get new time estimates from those team members for upcoming tasks, you can multiply their estimates by their individual fudge ratios. This will help you create a more accurate schedule for team projects. I think you’ll find that people tend to err in their estimates in a fairly consistent manner.
Achieve Reasonable Granularity
In order to make accurate estimates, it’s important that you break your tasks down to the right level of granularity. If your chunks are too big, you’ll overlook too many details. If your chunks are too small, you’ll get buried in low-level details, and you could spend more time estimating a task than it would take to just complete it; this is too much overhead.
For example, “Overhaul my website” sounds like a complex, multi-task project. This isn’t granular enough to make a reliable estimate. You’ll need to list the individual tasks needed to complete this project.
On the other hand, “Write mailing address on envelope” is way too granular. You could have completed this task in as much time as it took to list it and estimate it. This much detail only wastes your time instead of making you more efficient.
You should experiment to find the right chunk size where you can make the most accurate estimates. I’ll offer a couple pointers based on what works well for me:
The One-Sitting Rule. My estimates tend to be best for tasks I can complete in a single sitting. In practice this means about 2-4 hours per chunk. When I go less granular than that (bigger chunks), I miss too many details and grossly underestimate the time required. When I go more granular (smaller chunks), I list out too many details, I overestimate how long things will take, and I waste too much time creating and managing my to-do list instead of getting things done.
Compensate for Experience. If I’ve completed similar tasks many time before, my estimates will tend to be fairly accurate, so I might drop my fudge factor down to 1.2 or even 1.0. For example, I’ve written 700+ articles, so I’m pretty good at estimating how long an average article will take to write (3 hours is typical). But if I have to do something I’ve never done before, a fudge ratio of 2.0 or higher may be more accurate. The less experience I have with a task, the higher my fudge ratio needs to be.
Define Clear Task Boundaries
Make sure your tasks are clearly defined. Vague or nebulous tasks are hard to estimate.
If one of my tasks is “Update accounting,” I can’t be certain of what that includes. Does that mean balancing my checking account? Doing payroll? Filling out tax forms? Recording receipts? If I want to make a reliable estimate, I need a clear picture of what I’ll be doing.
You may find it helpful to list a few keywords for the components of an otherwise unclear task. You don’t necessarily need to estimate the time for each segment. You just need to be able to visualize what you’ll be doing. The keywords can help trigger the right imagery, so you can make a better estimate.
You should be able to quickly verbalize the first and last steps of each task. For example, when I see a task labeled “Write new blog entry,” I know that the first step is to pick a topic. The last step is to click the “Publish” button. If you can’t name the first and last steps of a task on your list, then your task doesn’t have clear boundaries. In that case you’ll need to take a moment to define those steps, or you’ll need to define your task a little more clearly, possibly by breaking it into smaller chunks. Good estimates require clear start/finish boundaries.
Be especially careful to consider what will be required to bring a task to 100% completion. If your task is to “Pay your bills,” does that end when you write the checks, when you deposit the payments in the mail (or complete an online payment process), when you file the paid bills in your filing cabinet, or when you balance your checkbook? Don’t forget to consider how long it takes to clean up and put away your materials. Even if you’re just making dinner, there will be dishes to attend to afterwards.
Reuse Estimates for Recurring Tasks
Once you’ve completed a recurring task, make a record of the time required for completion, so you can reuse that estimate in the future. When that task reappears on your to-do list, you can simply look up your old estimate. These estimates will be fairly accurate because they’re based on previous results, not previous estimates.
I recommend that you create an estimation list for your common recurring tasks. Here are two methods for doing that:
Method 1 (simple version). For a very basic estimation list, you only need to record a single figure for each task. Just note how long the task took to complete the last time you did it.
Your simple estimation list might look something like this:
Grocery shopping - 55 minutes
Make and eat dinner - 42 minutes
Vacuum house - 83 minutes
Wash, fold, and put away laundry - 75 minutes
And so on…
Once you build a good list of time estimates for recurring tasks, you can create a very reasonable plan for your day by adding tasks to your schedule.
Method 2 (detailed version). For a more complex version, you can record four figures for each task: (1) the number of times you’ve completed the task since you started keeping records, (2) your best (minimum) time to complete the task, (3) your worst (maximum) time to complete the task, and (4) your average time to complete the task. You can use these figures for making reliable estimates in the future; the min-max range tells you how reliable your estimates are likely to be. Whenever you complete each task again, take a moment to update your figures. In practice this won’t take much time at all, but you’ll end up with a fairly accurate list of estimates.
To update your average task time using this method, multiply (1) by (4), add the time required to complete the most recent repetition, and then divide the result by (1)+1. For example, if you previously completed a task 10 times, averaging 30 minutes per repetition, and the 11th repetition takes 35 minutes, then your new average is (10×30+35)/(10+1)=30.45 minutes. This method allows you to keep updating your average without having to record all of your previous task completion times.
If you record your best (minimum time) to complete a task, you can also use that to challenge yourself. Beating your previous record can motivate you to maintain a faster tempo. At the very least, try to beat your average time. Putting the clock on yourself can push you to work a little faster, especially for repetitive tasks that might otherwise seem a bit dull.
For most people I recommend Method 1. Method 2 is probably overkill unless you’re really committed to optimizing your time usage.
***
Learning to make better time estimates is a useful skill to develop, one that will serve you well for life. The methods above are actually quite easy to implement.
Becoming a better estimator may improve your life at the tactical level of daily time management, but be careful not to lose sight of the strategic level. Have you taken the time to define your life purpose? Are you setting the right goals? Are you working in the right career? Mastering low-level tactics won’t provide much value when your overall life strategy is nonsensical or nonexistent.
Even so, accurate estimation can benefit you across a variety of fields, so it’s a good skill to develop early in life. It’s still okay to develop this skill before you’ve achieved clarity at the higher levels of life purpose and long-term goals. Just be sure that at some point, you remember to attend to those higher levels, so you don’t merely become a faster rat on a treadmill.
What are your personal tips for generating good estimates? I invite you to share them in the forums. And remember, this is for posterity, so please… be honest. 
© 2008 by Steve Pavlina.
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译文:
如何准确估算时间
多数人不善于估算做事的所需时间.或许你估计需要一小时,实际上,你花了3-4个小时才完成.或者你为一项任务设定了30分钟,可你5分钟内就完成了.该怎么做从而使你善于准确估时呢?
这些是你可以用以更好估算时间的技巧:
计算你的胡扯概率
最佳的开始方式是测试你目前估算的准确度
制作一份待做事务的列表并完成这些事务.即兴估算并且记下完成每项事务你所需的预期时间.随着你一一完成这些事务,记录你实际所耗时间.然后以合计花费的所有时间,除完成诸多事务估算的所需总时.这就是你的胡扯概率.
举个例子,如果你估计完成某项事务列表需要12小时,但实际上却花费了15小时,因此你的胡扯概率即15/12=1.25.也就是说你要比预期的多花25%的时间才能完成这些事务.
若你采用各种事务测试胡扯概率,也许你会发现各项事务的胡扯概率存在差异,大概在0.1到10.0的幅度范围间.然而,对于需要数天去共同完成的团队事务,你会看到胡扯概率缩短至相对狭小的范围.当你平均足量事务,你的胡扯概率定于一个不变的数字.
我的平均胡扯概率大约1.5.这就是说,不论我即兴估算需要多长时间完成事务,平均一下,总归是我太乐观了,我得花费比事先猜测的多50%的时间才完成事务.对于任何特别单项任务,我的估算都不能更加准确.然而,如果我估计完成些许事务需要两天,那准需要大约3天.
一旦你知道自己的胡扯比率,你可以利用它为团体事务策划出更为准确的估算.只要合计你的即兴估算,乘以你所知的胡扯概率总数.这必定是相对准确的估算.
得知自己的胡扯概率比起初估算的更为准确,为某些事务估算时间时我总是很自信.我的即兴估算从未这样准确过.然而,以我的估算时间乘以胡扯概率所得的估算结果更接近实际所需时间.这帮助我更好的预算时间.
以我的胡扯概率为基础,我知道如果想在一天内完成大约8小时的实际工作,根据即兴估算(5:20=8小时/1.5)即得:我应该列下长打大约5小时20分钟的事务.不过每天都做这样校正似乎显得愚蠢,实际上完成的很好--远好于所列选的8小时任务,接着迫使自己工作12天,或者仅完成2/3的事务感觉很糟.自我破坏会把事态弄的更糟,这时浅意识明白我是在尝试不可能完成的事.
最好制作一张合理的事务列表,的确能在截止日完成,而不是痛责自己不善于估算时间.就算我的日程表看起来很简短,在截止日划掉最后任务时的感觉好极了.由于日常的差异,并不完全准确的,但总体上比我尝试的其他方法好的多,它激励出一种稳固的日常节奏,而不是超时超负荷的工作.
我推荐用至少长达10到20小时的事务计算你的首次胡扯概率.如果你只基于花费数时的事务计算,胡扯概率可能会不够准确.
当然在一段时间内,做一项事务而重复计算你的胡扯概率不失为一个好计策.每次四回就可以了.当你的常规工作变更时就更新它,实为明智之举.比如当你开始一项新项目或换了公司或者行业.
如果你需要更多的详细数据,你可以计算不同工作的不同胡扯概率.我个人没这么做过,但如果你觉得不同的工作会产生不同的胡扯概率,那么这么做是不无道理的.例如,如果你是一个学生,完成数学作业需要0.9的胡扯概率,但完成学期论文需要1.7的胡扯概率,你可能需要保留各项胡扯概率以达到更有效的估算.
如果你管理一个团队，你可以为团队的每个成员计算他们的胡扯比概率(成员参与或不参与都可).向成员索要完成一系列工作的估计时间,测试真正的所需时间,为每个成员计算胡扯概率.每当你得到这个队伍成员即将开展工作的新的估计时间,你可以将他们的估算乘以他们的各自的胡扯概率.这可以帮助你算出一份更准确的团队项目行程表.我觉得你会发现人总在一定程度上误信自己的估计.
达到合理量度
为了准确估算,细分你任务的量度指标很重要.如果你的量太大,你将忽略很多细节.如果你的量太小,你将被细枝末节埋没,你估算的耗时将比你完成任务的所需时间还要多.这太过头了.
例如,"检修我的网站"听起来是项很复杂繁琐的工程.这不够量化以至于无法做出可靠的估算.你得列下完成这项工程所需的各项任务.
另一方面,"将邮件地址写在信封上"这个太量化了.你可以在把它列表并估算的时间内完成这个任务.这样的细节工作只会浪费你的时间,而非使你的工作更有效率.
你应该做个实验,以寻找自己足以做出最准确估算的确切量度.我将根据适合我的工作在此提供一些指点:
单设规则.这个估算对那些只要设定一次的任务是顶好的.实际上意味着每个大约2到4小时的量.当执行粒度比(更大量)小的,我因错过很多细节而粗略低估所需时间.当粒度比(更小量)大,我因列出所有的细节而高估这些事所需的时间,我因此花了更多的时间制作和管理待做列表,而不是花费于完成这件事.
依靠经验.如果你曾多次做过相似事务,你的估算将相对准确,所以我将胡扯成因降到1.2甚至1.0.例如,要写一篇700字的文章,我很擅长估算写一篇文章一般所需的时间(通常3小时).但如果你要做以前从未做过的事情,2.0或者更高的胡扯概率更为准确.你对事务的经验越少,你的胡扯概率就越高.
定义清晰的事务范围
确定清晰定义你的事务.摸棱两可的事务定义将难以估算它所需的时间
如果我的某项事务是更进统计,我不确定这包括什么.平衡我的支票户头收支?制作工资单?填写税收表格?记录发票凭证?如果你想做一份可靠的估算,我需要所做何事的更明确陈述.
你会发现对不清楚的事务列出些成分关键词是很有帮助的.你不需要估算每个部分,只要能预见所干何事便可.关键词将帮你产生正确的联想,因此你可以更好的估算.
你应该迅速描述每项任务的第一步和最后一步.例如,当你看到一个标签是"纂写新的开篇博客"我知道第一步是选个话题,最后一步是按下"发布"的按纽.如果你无法在你的列表上命名你任务的第一步和最后一步,你的任务就不具备清晰的范围.在这样的情况下,你需要花片刻定义这些步骤,或者你需要将这些事务定义的更清楚,尽可能的细分到较小的量度.好的估算需要清楚明了的开头/结尾定义范围.
当考虑100%完成任务所需的时间时请务必小心.如果你的事务是"支付帐单",是否在你写帐目的时候就结束了.何时从邮件中取回款项(或者完成在线支付程序),何时在你的内部文件填写支付帐单,或者你何时平衡你的帐本收支.不要忘记考虑清理和摆放材料所需的时间.就算你做顿晚餐,结束时你总得洗碗.
对号入座
当你完成一个再度出现的事务,记录完成的所需时间,你以后可以重新使用这个估算.当这个任务重新出现在待做列表，你可以简单的看下你过去的估算,这些估算相对的准确,因为是基于先前的完成结果而非先前的估算.
我向你推荐制作一份通常重复出现事务的估算列表,做这样的估算表有以下两个方法:
方法一(简单版本).制做基本的估算列表,你只需记下每项事务的单个数据.只要注意上次完成这些任务你所花的时间
你的简单估算列表如下:
购物-55分钟
做饭和吃饭-42分钟
清理房间-83分钟
清洗衣物,折叠衣物.摆放衣物-75分钟
等等
当你制作了一份不错的常做事务的估算列表,就可以制定一套很合理的日常计划,并在你的日程表附加别的事务.
方法二(细节版本).制作更为复杂的版本,你得记下每项事务的四组数据:(1)自你记录这项事务起它所执行过的次数,(2)完成这项任务的最佳(最少)效率,(3)完成这项任务的最低(最多)效率,(4)完成这项任务通常所需的时间.这些数据可以用来在以后估算时间,最小到最大范围告诉你,你的估算很可靠.当你再次执行这些事务,花片刻更新数据.实际上,这不占多少时间,但你得到了一个相对准确的估算.
更新你完成事务平均耗时的方法.以1乘以4,加上最近一次完成的耗时,以这个结果除(1)+1.例如,若你先前曾10次执行某项事务,平均重复执行的时间为每次30分钟,重复第11次时花费35分钟,即得你的最新平均值为(10x30+35)/(10+1)=30.45分钟.这个方法可以更新你的平均耗时,而不需要记录你先前所有事务的完成时间.
如果你记下自己完成的最好成绩(最短耗时),可以用此挑战自己.超越你先前的记录,激励你保持更快的速度.最起码,尝试快于平均耗时.对自己计时推进你稍快的完成,特别是那些重复着而又冗长的事务.
我向大多数人推荐方法一.方法二可能难度太高,除非你对自己把握时间很自信.
***
学习更好的估算时间是自身发展中很有用的技巧,一劳永逸.以上的方法易于执行.
成为一个更好的估算师,可以从日常安排的战略标准,提高你的生活质量,但注意切勿忽略策略标准.你有花时间定义你的生活目的么?你有为自己设定正确目标么?你有从事合适的职业么?当你的总体生活策略不具备意义或者形如虚设,掌用低水准的战略不会给你带来价值.
即便如此,正确的估算能使你在各行业都收益非浅.这是得尽早掌握的好技巧.在你达到明确的高层次的生活目的和长期目标之前,掌握这个技巧还为时不晚.只要确定某几点.你得记得专注于这些更高的层次,这样你不至于成为一只飞快踩车轮的仓鼠.
你有哪些高效估算的个人计策呢？我邀请你到论坛分享它们．记住,这是为了后行者,敬以诚为贵
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