Your Whiteboard and Post-Its Aren’t Kanban

Kanban is an incredibly useful productivity tool, initially developed in Japan on automobile manufacturing lines. It has since become a widely adopted practice, including in software development and project management. Or has it?

That cute, simple tool you have that uses post-its, or skeuomorphic representations of them, to keep track of the state of some task or project? It’s not Kanban. To paraphrase Bill Hicks: No no no, I know you think it is. But it’s not.

What you have is a useful means of task and project management. It might be awesome. It might be saving you effort, time, and stress, and actively making your life better. I’m sure it’s a good tool, Brent. But it likely has nothing to do with Kanban.

To be clear, that’s fine. There’s no rule that says Kanban is useful to solving your problem, or that you ever need to use it. It’s just, you know, words have meanings. And the meaning of Kanban is all about inventory management. It’s true that you totally could be using post-its on a whiteboard to track inventory. But you’re probably not.

In both your task tracker and in Kanban, the card represents something. That is, the card itself is not relevant, but it represents a thing that you care about. In your tool, it’s representing some task that someone needs to do and the state that the task is in. This helps you to understand and communicate key information across all of your tasks, projects, and teams. I can see why you find this useful. Heck, I find it useful. I’m using it to track the state of this article, for instance.

In Kanban, the card represents something completely different: The need to refill inventory. At its simplest, you use cards to denote the minimum allowable inventory in a system, such as car doors sitting at an installation station. You do so by literally placing a card on the door at the minimum level. You pair these cards with separate rules about the maximum allowable inventory. Now each of your inventory pools (doors, engines, seats, etc.) have maximum and minimum levels — if the inventory gets low enough, the installer encounters the card and orders a refill, which itself is never above the maximum allowed. As you operate the system you tune it over time to make sure your min and max levels are right.

For most of your work, you can ignore the card and focus on what’s in front of you, but as soon as you encounter it, you must take action. This gives you two features that are otherwise lacking: You get to ignore the card and focus on your work for the majority of the time, which is incredibly important for productivity, and you also get to explicitly separate the process of optimizing the inventory pools from how you consume them. You can always be in the moment when you do the work.

On first blush, you might think to yourself that this doesn’t sound very useful. I mean, how much of your life is really affected by inventory problems? Pffft. Literally all of it. You deal with this constantly in your car, for example; its maker decides on your maximum fuel level (the tank is fixed in size), and you never want to run out of gas, but instead of a card you have a light on your dash when it gets too low. Obviously every grocery store and restaurant has to think about this, but so do banks (envelopes, paper, checks), mechanics (parts, tools), and coffee shops (coffee, chairs — yes, chairs).

You have personal inventory problems, too. We keep hearing about these magical fridges that will order milk for us automatically (but are more likely to be used in a DDoS); Amazon has released one-touch buttons that enable us to trivially order new inventory; and most of us have experienced the ignominy of running out of a key supply at just the wrong time, such as when using the toilet. To see these problems for what they really are, you need to step into a different mental model, a new world.

You need to step into the world of inventory. Rather than seeing everything around you in terms of work to be done, see it in terms of pools of inventory to be shifted, consumed, and refilled. It’s not necessarily “better”, but it is often enlightening. Kanban got created as a tool specifically for increasing the efficiency of such a world, and only makes sense when you’re in it. In fact, the cards themselves aren’t important at all — there are plenty of different triggers available.

It might shock you to realize just how much of your life would be improved by viewing the world this way. Suddenly all of those latent tasks that are sudden emergencies when you run out of something become simple efficiency problems that are easy to model and solve. In my last few years of experimenting with this in my personal life, I’ve built many triggers into many of our inventory pools. None of them are cards, but they are all closer to Kanban than your Trello board.

For example, we go through a lot of granola in my house. Our means of ensuring we never run out is to have two containers, about the same size. We always pour breakfast from one and refill from the other, and the emptying of our refill container is the trigger that causes us to buy more granola.

We keep one in-use and one unused toilet paper roll in each bathroom, plus a cache in a closet. Emptying the in-use triggers using the extra roll, which triggers pulling another roll from the cache. If that is the last roll there, pulling it triggers buying more.

In each of these cases, we’ve set up inventory pools that match how long it takes to refresh them. For example, our granola containers are sized that so that we don’t go through a whole container faster than it takes us to buy more. We never run out of toilet paper, but we don’t have to dedicate a room to storing it.

This perspective also allows us to recognize when we are missing a trigger to refill inventory, allowing us to shift the conversation from personal blame to process improvements. For example, in a bid to teach our kids to self-regulate their sugar intake, we’ve started making our own fruit yogurt and letting them add sugar, rather than buying pre-made fruit+sugar yogurt. We kept running out, though, because it took a day to thaw frozen fruit. We didn’t have an appropriate trigger to start this task at the right time. Having recognized this problem, we created one (I get frozen fruit out to thaw when we have about one meal left of pre-mixed yogurt), and on first blush, it seems to be working. We haven’t yet integrated it with one that buys more yogurt on the right cycle, though, so it’s not yet a complete system.

These are examples of using non-card triggers for Kanban-style inventory management. It’s the triggers that matter, not using cards to represent them. If we tended to have larger collections of unit inventory, cards might be appropriate. E.g., I usually buy razor blades in bulk, and it might be appropriate to label one of those blades with a card to trigger repurchase when I reach it in my stack. Here I’d have to find the right optimization between managing a large inventory, finding the right trigger, and getting the lowest cost per blade (which requires buying in bulk). Combine that with the fact that I usually use an electric razor (which means I rarely assess the state of my blade inventory) and the likelihood of making an inventory mistake goes up, thus increasing the value of a trigger-based system.

For all that I love tools like Trello, and systems like Kanban, I’m not sure they can ever actually be used together. That is, I think we have a whole industry of tools built to model a specific kind of problem, which are instead useful for many things but specifically not the problem they’re meant to exemplify.

The beauty of Kanban is that it’s out in the world, where your work is. (Don’t be confused into thinking that that board or those cards are your work; they just represent it.) I’ve been trying for years to build a Trello board, or some equivalent, that enables an inventory-oriented view on what I’m trying to do, but I’ve not yet succeeded. For instance, [WIP limits] mean something completely different when they represent tasks instead of inventory. That doesn’t mean they’re useless, just not useful for the same reasons.

My recommendation is that you enjoy your task management system, and continue to get what you can out of it. Maybe just stop calling it Kanban. At the same time, though, ask yourself: Where are the inventory pools in my life? What do I run out of, and how can I build triggers at the right point to prevent that? How does my world change when viewed this way?

Most of all, get out into the world. That’s where the work is.