Practical guide

Estimating your own habits well

LifeTime measures nothing — it extrapolates what you give it. The quality of the result depends entirely on the quality of your estimates. Here's how to make them substantially less wrong in a few minutes.

Why our estimates are bad

Estimating an average duration from memory is an exercise the human mind gets wrong in fairly predictable ways. Three mechanisms come up constantly.

We answer as the version of ourselves we prefer

Socially valued activities — sport, reading, cooking, time with family — are systematically overestimated. Less flattering ones — phone, screens in general, television — are underestimated. This isn't dishonesty: we simply remember the times we made the effort better than the times we didn't.

We answer for an ideal week

Asked for an average, people spontaneously describe a good week rather than a typical one. The weeks where the workout was skipped, where no reading happened, where everything slipped — those drop out of the mental average even though they are part of it.

We forget the small pieces

Activities fragmented into dozens of short sessions are massively underestimated: glancing at your phone for two minutes, forty times a day, leaves no memory of duration but adds up to over an hour. Long, identifiable blocks — a training session, a film — are estimated reasonably well.

Look for evidence, not memories

The single best habit is to replace introspection with real data wherever any exists. Many activities leave a trace:

• Phone. Your phone already keeps count. "Screen Time" on iPhone, "Digital Wellbeing" on Android — both give a daily average over the week. It's the most reliable reference in the whole quiz, and usually the most surprising.
• Video games. Steam shows hours per game, consoles publish a yearly recap, and most platforms keep a history. Adding up the big titles is enough to pin the order of magnitude.
• Series and films. An episode is 25 or 45 minutes, a film about two hours. Count episodes per week rather than estimating hours directly, then multiply — far more reliable.
• Commuting. Your route to work has a known duration. Double it, multiply by the number of days worked, then add some margin for everything else.
• Sleep. Bedtime and wake-up time give the hours in bed. Trim a little for falling asleep if you want to be strict.
• Work. Start from your contract or your actual hours, not your impression. Don't forget regular overtime.

Count a full week, weekend included

For questions asked per week, the right method is to walk mentally through all seven days rather than announcing a single global figure. Many activities have a very different rhythm at the weekend: gaming, going out and watching series often cluster into two days, while commuting disappears entirely.

For questions asked per day, think the other way round: your average must include the days where you did nothing. An hour of cooking five days out of seven averages forty-three minutes, not an hour.

Watch out for double counting

LifeTime treats each category separately and detects no overlap. If you're on your phone in front of a series, the time counts in both.

That isn't necessarily a problem — it's arguably fair, since you really are doing both. But you need to know it, and above all stay consistent from one category to the next. The worst case is being scrupulous about one category and generous about another: the gaps between categories, which are the main value of the result, then become wrong.

Using periods properly

This is the most powerful feature of the quiz, and the most often ignored. By default, an activity is counted from your birth at your current rate — which is absurd for most of them.

Set a real starting age

Add a first period at zero hours running up to the age you genuinely started. Without it, the quiz assumes you've been using a phone since birth.

The categories most affected are phone, video games, work, grocery shopping, housework, admin and going out.

Mark the real breaks

There's no need to slice finely. One or two cuts are enough, placed where your rhythm genuinely shifted:

• starting work, which changes work, commuting and going out;
• a child arriving, which changes more or less everything;
• a move that substantially changed your commute;
• the arrival of the smartphone in your life, for the phone category;
• lastingly stopping or taking up a sport.

Beyond three or four periods you're adding false precision: you end up estimating old rhythms you no longer remember, and uncertainty grows faster than detail.

Don't chase precision that isn't there

The calculation is deterministic, but its starting point isn't. Hesitating between 2 h and 2 h 15 doesn't matter: the resulting difference amounts to weeks across thirty years, far below the error in your own estimate.

Round freely, and put your attention on the categories that weigh a lot. Being half an hour a day out on sleep moves the result far more than being off by a factor of two on creative hobbies.

A good way to go about it

• Do a quick first pass, purely to discover the eighteen questions.
• Open your phone's screen-time stats before the second pass.
• Start again taking your time, adding periods where it genuinely matters.
• Look at the gaps between categories first, not the absolute values.
• Note whatever surprises you: that's where the useful information is.

Since nothing is stored, starting over costs nothing and overwrites no history.