What counts as a good completion rate

Completion rate is the number worth watching, and almost nobody knows what a good one looks like. People assume higher is better all the way to 100, which is wrong in an interesting way: a habit you complete every single day for months is a habit whose target is too low to be doing anything.

The useful range for a habit you are actively building sits somewhere between 75 and 90 percent. Below 75 the habit is failing often enough that the cue or the target needs changing. Above 90 for several months, and either the habit has gone automatic, in which case congratulations and take it off the list, or the target is set below the level where it produces an effect.

There is a second reason to care about the exact number: it is the only honest way to compare two habits. A 40 day streak on flossing and a 12 day streak on writing are not comparable, because one is trivially easy and the other is not. Completion rate over a rolling window is, and it also survives the interruptions that make streaks unreadable.

This guide covers the window length to use (30 days, mostly), how the number should differ by habit type, when a falling rate means change the target rather than try harder, and the two ways completion rate can be gamed by a tracker that counts skipped days as neutral.

Outline

Status: outline. The introduction above is finished copy. Everything below is the section plan for the full draft, targeted at about 1 400 words.

1. Why 100 percent is a warning. Targets set below the effective level.
2. The 75 to 90 band. Where an actively building habit should sit.
3. Choosing the window. Rolling 30 days, and when 7 or 90 is better.
4. Rates by habit type. Automatic, maintenance and building habits have different targets.
5. Falling rates. Diagnosing target, cue or fit, in that order.
6. How the number gets gamed. Skipped days, scheduled days and the denominator problem.