Saturday, February 21, 2009

Pizza Points - story estimation made round!

There's two commonly used methods for agile estimation Story Points and Ideal Programming Somethings, commonly days or hours. Both methods have their merits with some bias towards Story Points (SP) from Mike Cohn and various other well known names although Ideal Programming Somethings seems to be more commonly used by the teams I've spoken to.

There seems to be quite a bit of confusion regarding how they relate and how both terms relate to hours. To remedy some of this I want to propose a new system, Pizza Points, that is driven by an easy to explain intuitive and rich metaphor.

Lets look at the similarities between work and pizza as used in the following discussion.

  • Pizza is round, work tends to be circular.
  • Pizza can be filling and deeply satisfying, as can work.
  • Pizza comes in different sizes, as does stories and tasks.
  • Pizza can have lots of varying and interesting fillings, work can be filled with many intresting things.
  • As we mature we can eat more pizza and as we learn a domain and tools we can tackle bigger tasks.

Depending on the peculiarities of your favourite pizza parlour the size and form may vary, maybe you have children, normal and family, maybe the range is small, medium, large, and extra-large often it's round and sometimes you get oddly square bites. There's no guarantee that a small pizza is the same size between to different places and there's likewise no sense in assuming that a pizza point is equally sized between two teams. That said, if you stick to one place, keep your team intact, any given size will overtime be quite consistent.

So how do we get started using Pizza Points?

We have to start by establishing some sort of baseline size, no diffrent from the initial sizing of story points. Find a fairly small, easily graspable story discuss the criterias for done and label it "children", "small" or why not, one. Continue estimation by thinking about the relative *size* not filling, give them descriptive names, standard, family, 2, 3, 5, 8, 13, 20, 40, 100, xxx-large.

It's as easy as that. The thing to remember is that size is actually a constant but the filling might greatly influence how much we can eat. I like pizza and can eat quite a lot given toppings like different cheeses, ham, pineapple for example. Give me anchovies and you'll have me struggling an evening to come close to finishing even a child size bite. The size haven't changed, my aptitude and motivation did.

If you're the one placing orders and want to get as much pizza eaten as possible during any period of time it can be wise to ask your team for their taste preferences. But real life sometimes dictates that we put anchovies on their plate, that's a big responsibility.

To summarize, think size not filling, match fillings to team, expect size to vary depending on team. Also expect mature, adult, teams to eat more than children.

And don't forget to order planning pizza as a reminder during long estimation sessions.


  1. This comment has been removed by the author.

  2. I do like the last line... something to keep in mind as our planning sessions tend to grow long.

    As a metaphor I think that you are quite right. Most of the time we tend to look at how "much" work that is to be done, and not "what kind of work" and if that team is suitable for it. I recall Henrik Kniberg talked about this during the Scrum Gathering, and he proposed that the PO's "sold" their stories during one day of planning. Almost like putting them out for the highest bidder. And as the teams wasn't "set", new ones formed around "interest" instead of "delegation" each and every sprint.