Tag Archives: estimating

Estimates: Time-Based vs Point-Based, and when to use them.

There are two general methods for software estimates, time-based and point-based. Here are some tips on when to choose either one.

Time-Based Estimates

Time-based estimates can be tricky. They are the simplest style of estimate and that simplistic nature lends engineers to treat them flippantly. Just about every engineer has said “That’s easy, it’ll take 15 minutes” about something trivial, and then spent a full workday working on it. Time-based estimates get a bad rap from engineers, because they feel punished for missing them. Project managers like them because planning work is simpler.

Time-based estimates work best for near immediate-priority bug fixes / feature requests, and costing and budgeting breakdowns.

Point-Based Estimates

Points-based estimates are a common model in Agile shops, and are largely the same except in terms of flavor when they are requested in terms of t-shirt sizes or Fibonacci series values. They are meant to be quick estimates that give a sizing gauge for the feature without the negativity associated with a missed estimate. Points-Based estimates get a bad rap from project managers, because the statistical approach to ‘backing into’ the time something takes is not accurate enough to get an ‘on-time’ delivery of anything. Engineers like them because they don’t feel as beholden to them.

Point-based estimates work best for high-level estimates of long-term work, or as a quick way to gauge consensus between engineers.

When To Use Them

A project team will generally follow a particular methodology (Agile, SAFE, Waterfall), so you may be held to the preferences and norms of that group, but in general, follow these guidelines for successful estimating.

  • When to use a Points-Based Estimate
    1. The amount of time dedicated to estimating is low.
    2. The priority on the work is variable; your product owner will use your estimate to assist in determining its priority.
    3. Engineers have substantively different approaches to the work, or the work is largely exploratory.
    4. Your dev-to-release cycle is fast.
  • When to use a Time-Based Estimate
    1. The work is your next immediate priority item.
    2. You will use the estimate to directly assess cost.
    3. There is an understood and correct way to do the work, and will not drastically change if done by one engineer or another.
    4. Your release cycle is slow, or singular.

Two Rules to Estimating Software Features

OK, you’re a software developer, and someone’s asked you to quick look at a feature, and give them an estimate on how long it’s going to take to develop. For this example, I will refer to that feature as ‘SuperFeature’, and we will have two estimating developer examples; Gina, who examples good estimates, and Lisa, who examples less good estimates. Priya is our product owner, and since Priya owns the product, good estimates give her the information required to make a intelligent decisions. Well-formed estimates enable her to prioritize work well, and manage expectations of customers and stakeholders.

Here’s two rules to estimating features successfully.

Rule 1: Your estimate should represent doing the ‘work done in a vacuum.’

It is counter-intuitive to estimate work in this way, but creating an estimate, as if that work is being done in a vacuum is the best way for your product owner to assign the feature a priority.

Example:

Gina, who estimates in a vacuum – “SuperFeature will take about 2 weeks to do.”

Lisa, who estimates based off of her current workload – “I will need 6-8 weeks to do this.”

In the first case, Priya knows how long the feature will take to develop. She knows that Gina and Lisa are both working on very high priority items, so she gets Liam to work on that feature.

In the second case, the Priya knows how long Lisa will take to get it done, but has very little awareness of the what priority Lisa is putting on the work. At next week’s stand-up, imagine Priya’s surprise to know that Lisa hasn’t even started work on it yet!

The lesson: Your product owner owns priority of the features. An estimate should give your product owner the information required to set that priority.

Rule 2: The larger an estimate, the more detail it needs.

If your feature is large, your product owner needs to know and understand why. In order to understand the work needing to be done, it should be broken down into tasks.

Example:

Lisa, who doesn’t break the work down – “SuperFeature will take about 4 months to work on.”

Gina, who realizes the work is complicated, and Priya needs to understand the details. – “In all, SuperFeature will take about 4 months. We’ll need 3 days to start building the catalytic converter, and then a week to refit and install the Whizzbang…” etc, etc.

In the first case, it’s hard to really even start the work, or even know how to break it up. Is it 4 months altogether? Can you break the work apart? Can you create multiple work streams?

In the second, Gina gives Priya all the details she needs to break up the work accordingly. She also does so succinctly, so that ordering tasks and dependencies are clear.

Following the two rules above will help make your estimates more valuable and your relationship with your product owner more beneficial.