In the world of programming, there are lots of rules to highlight how bad developers are at estimating the time it will take to finish a project.

It’s so difficult to estimate time accurately, that the rules are even sarcastic about it.

The first rule of thumb is to estimate how long each task within a project will take, add all the time together…and then double it.

There’s also the 90-90 rule, which states:

The first 90 percent of the code accounts for the first 90 percent of the development time. The remaining 10 percent of the code accounts for the other 90 percent of the development time.

— Tom Cargill, Bell Labs

And then Hofstadter’s Law says:

It always takes longer than you expect, even when you take into account Hofstadter’s Law. — Douglas Hofstadter

The theme is that no matter how careful you are, people are terrible at estimating the time needed for complicated tasks.

And while we’re happy to acknowledge that programming is complex, we don’t always apply the same prediction principles to an even more complex problem:  The behavior of people.

This is why I came up with the idea for the T.U.C.K Rule, which stands for:





This speaks to the span of time between when a customer indicates they want to use your product or service and when they actually start using it.

The idea is that regardless of what a prospective customer does or says, it will always take way longer for them to get started than you expect.

How much longer will it take? Like programming it’s hard to say for sure, but a good rule of thumb is to at least double it.

In other words, if a customer indicates they’ll be ready to start “next week”, plan on at least two. If they say “next month” it may be next quarter. Etc, etc.  

What makes the T.U.C.K. Rule extra tricky is that unlike internal projects the inputs for these estimates come from the customers themselves. You can watch their actions and ask them questions, but you’ll never have insight into what’s happening with them behind the scenes. You have to wait and watch, and then react and adjust.

And how you interpret that data can have a big impact on how you project sales. If you take every customer action at face value you’ll end up with some wildly optimistic projections.

But If you keep the T.U.C.K. Rule in mind it can help curb those expectations and keep them a little closer to reality.

So, the core question here is why are these estimates so off?

Why Are We So Wrong About Time?


(Time keeps on slippin’ into the future…photo via Aron Visuals)

Time estimates for tasks generally come from an honest but deeply flawed place. In the same way a developer believes creating that new feature will only take “a few days max”, customers genuinely believe they’ll be ready to start “next week”.

The fact that in both cases their estimates are optimistic is less about their intentions and more a result of how our brains are wired.

There’s a name for how this behavior plays out with people called The Planning Fallacy.

The Planning Fallacy describes people’s natural tendency to be overly optimistic about predicting the time they need to complete tasks.

There are several theories on why this happens:

  • We put too much focus on best case scenarios, rather than exploring realistic or typical results based on past experiences.
  • We have a hard time accurately remembering past experiences. When we remember past situations we’re inclined to take too much credit for the parts that went right and put too much blame on external forces for what went wrong.
  • We suffer from “wishful thinking” where our optimism is driven by the result we hope will happen.
  • We also want to make a good impression with others. Faster sounds better.

In reality, we know there are all sorts of factors that slow down decisions and keep customers from starting something new:

  • Discussions with other team members or stakeholders to get signoff
  • Time to review alternate solutions
  • Their own existing work commitments
  • Sickness, vacations, family obligations, and other normal life stuff
  • The lingering consideration to do nothing at all

Any one of these can have a huge impact on making a final decision. Combine two or more and you can imagine how fast the delays add up.

Why T.U.C.K.?

Warning: brief sports content ahead…

If you follow the NFL you may have come across their version of the “tuck rule”. The now defunct rule stated that when a quarterback’s arm was moving forward with the ball, even if the QB attempted to tuck and hold onto the ball, it was still treated as a pass. This meant if the ball came loose while trying to tuck it, the play would result in an incomplete pass not a fumble.

While this annoyed and confused fans, the point was to keep referees from needing to interpret the intent of the quarterback.

That’s the relevance here.

No matter how a situation appears, you can’t actually predict what’s going to happen. A customer who wants to “throw”, can take the same actions as one that’s about to “tuck”. Even if they tell you their intent, you can’t rely on that data.

Now, you may be asking yourself, “Is this tenuous analogy between an obscure football rule and business behavior a lame attempt to get accidental clicks from people looking for Super Bowl content?” Possibly.

Was the T.U.C.K. acronym basically just some random idea for an acronym that popped into your head? Definitely.

Will this concept actually remind me to avoid misinterpreting my customers’ behavior? Hopefully.

Bonus Business Acronym: R.U.L.E.

If you love a good acronym as much as I do, then why stop at one? With such a tricky topic, you may need a backup for times when T.U.C.K. doesn’t kick in.

R.U.L.E. provides another guideline to follow for predicting the accuracy of sales based on customer time estimates.





It doesn’t mean your customers want to flake on you, but you might want to pad your expectations around when the work will get started.

If you can remember T.U.C.K and R.U.L.E. you’ll do even better at avoiding overly optimistic sales predictions.

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