Methodology

How LifeTime calculates your years

LifeTime tells you "you've spent 9.4 years sleeping". This page explains exactly where that number comes from, what it measures, and — more importantly — what it doesn't.

What the number actually means

A "year" in LifeTime is not a calendar year. It is the equivalent of 365.25 full 24-hour days spent on nothing but that one activity, laid end to end. Sleeping eight hours a night doesn't consume one calendar year in three — but added up, it does account for a third of the time that has passed.

That's why the totals look large at first glance. They are expressed in absolute time, not as a share of your waking hours or your free time.

Step 1 — what you provide

Every question asks for an average duration, either per day or per week, depending on the activity. Sleeping, eating and bathroom trips are asked per day; sport, reading and grocery shopping are asked per week, because most people do them only a few times a week and naturally think at that scale.

You can enter hours and minutes. Both are merged into a single decimal value before anything is calculated.

Step 2 — convert to a weekly rate

Everything is reduced to hours per week. A daily figure is multiplied by seven; a figure already given per week is taken as is.

hours_per_week = hours_per_day × 7
(or the weekly value directly, depending on the question)

Step 3 — extend across the years lived

That weekly rate is then applied across the period in question, at 52 weeks per year.

total_hours = hours_per_week × 52 × years_in_period

Step 4 — convert to years

The hour total is divided by the length of a full year — 365.25 days of 24 hours, or 8,766 hours. That extra quarter-day is what produces leap years.

years = total_hours ÷ (24 × 365.25)
years = total_hours ÷ 8,766

A worked example, for someone aged 30 who has always slept eight hours a night:

8 h/day × 7 = 56 h per week
56 × 52 × 30 years = 87,360 hours
87,360 ÷ 8,766 = 9.97 years

When a total falls below one year, LifeTime switches to days rather than showing "0.3 years", which means nothing to anyone.

Periods: when your rhythm changed

Nobody keeps the same rhythm for life. So you can split any activity into several age brackets, each with its own duration. Each bracket starts where the previous one ends, and the first one starts at birth.

In practice, if you enter "from 0 to 12: 0 hours per week" and then "from 12 to 30: 10 hours per week", only the last eighteen years are counted. This is the mechanism that lets you set the age at which you actually started an activity — which matters enormously for video games, phone use and work.

Worth remembering: by default, an activity is counted from birth. If you didn't own a phone before fifteen, you need to add a first period at zero hours, or the total will be badly overstated.

The one exception: work and study

A school year doesn't last twelve months. So between ages 0 and 18, LifeTime counts only eight months out of twelve for the "working or studying" question, which automatically removes the four months of school holidays each year.

The adjustment applies only to the slice of a period genuinely below 18. If you enter a single rate from 6 to 30, the first twelve years are reduced and the following twelve count in full. No other category gets special treatment.

Why the radar uses a square-root scale

On an ordinary chart, sleep and work flatten everything else: both often exceed ten years, while reading or creative hobbies are measured in months. Every smaller category would end up crushed against the centre, unreadable.

So each axis is drawn at a radius proportional to the square root of the ratio between that category and your largest one:

radius = √( category_years ÷ largest_category_years )

This keeps the ordering intact — whatever is bigger stays bigger — but compresses the top of the scale and lifts the bottom. One direct consequence to keep in mind: axis length is not proportional to time. An axis twice as long represents four times the time, not twice.

The rarity tiers

All four result views (radar, RPG sheet, loot, wings) share the same thresholds, applied to that square-rooted value. Expressed as a share of your largest category, they work out to:

Legendary — from roughly 72% of your largest category's time
Epic — from roughly 36%
Rare — from roughly 12%
Common — below that

These tiers are relative to you alone. They compare you to no average, no other user and no external dataset. "Common" doesn't mean "not much" — it means "small next to your own maximum", which is almost always sleep.

What the method does not do

These limits are deliberate, and worth knowing before taking any result seriously:

One average per period. You give a typical rate, not a log. Busy weeks and quiet weeks cancel out, and nothing distinguishes a Saturday from a Tuesday.
No overlap handling. Time on your phone while watching a series is counted in both categories. The sum of all your categories can therefore exceed the time you have actually been alive.
52 weeks a year, not 52.18. The rounding removes about three tenths of a percent from the total — far below the margin of error in your own estimate.
No external data. LifeTime uses no reference statistics, no national averages and no corrections. Everything comes from what you type in.

Put plainly, the accuracy of the result is exactly the accuracy of your answers. The calculation itself is deterministic: the same answers always produce the same result.

Where the calculation runs

Entirely in your browser, in JavaScript. No answer is sent to a server, none is stored, and nothing survives closing the tab. That's also why there are no accounts — there is nothing to save.