About

A human life of 80 years contains roughly 29,200 days, 700,800 hours, and 2.5 billion heartbeats. Most people cannot intuit where they stand within that span. This tool computes P = (t_now − t_birth) ÷ (t_end − t_birth) × 100 using millisecond-precision timestamps from the Date API, then decomposes the result into years, months, weeks, days, and hours both lived and remaining. It estimates physiological counters - heartbeats at 72 bpm, breaths at 16 /min, sleep at roughly 33% of elapsed time - using population-average rates from WHO actuarial references. The progress bar updates every second.

Formulas

Life progress percentage:

P = t_now − t_birtht_end − t_birth × 100

where P = life completion percentage, t_now = current timestamp in milliseconds, t_birth = birth timestamp, t_end = projected death timestamp (t_birth + L × 365.25 × 86400000), L = expected lifespan in years.

Estimated heartbeats lived:

H = t_elapsed × 72 × 60

where t_elapsed = hours lived, 72 = average resting heart rate in bpm.

Estimated breaths:

B = t_elapsed × 16 × 60

Time asleep:

S = t_elapsed × 0.33

where 0.33 represents the average fraction of life spent sleeping (~8 hrs/day).

Reference Data

Life Stage	Age Range	Approx. % of 80-Year Life	Key Characteristics
Infancy	0 - 2	2.5%	Rapid neural development, motor skills
Early Childhood	3 - 5	3.75%	Language acquisition, socialization
Middle Childhood	6 - 12	8.75%	Formal education begins, cognitive growth
Adolescence	13 - 19	8.75%	Puberty, identity formation, prefrontal cortex immature
Early Adulthood	20 - 35	20%	Peak physical performance, career establishment
Midlife	36 - 55	25%	Career peak, metabolic decline begins ~40
Late Adulthood	56 - 70	18.75%	Retirement transition, bone density loss
Old Age	71 - 80+	12.5%	Wisdom consolidation, chronic disease risk
Physiological Benchmarks (Population Averages)
Heart Rate	60 - 100 bpm		Average resting: 72 bpm
Respiratory Rate	12 - 20 /min		Average: 16 /min
Blink Rate	15 - 20 /min		Average: 17 /min
Sleep	7 - 9 hrs/day		~33% of total life
Steps per Day	4,000 - 10,000		Average: 6,500 /day
Global Life Expectancy by Region (WHO 2023)
Japan	84.3 years		Highest globally
Switzerland	83.4 years		Europe leader
Australia	83.3 years		Oceania leader
United States	77.5 years		Below OECD average
Brazil	75.3 years		South America average
India	70.8 years		Rapid improvement trend
Nigeria	54.7 years		Sub-Saharan Africa
Global Average	73.4 years		Up from 66.8 in 2000

Frequently Asked Questions

The tool uses a user-defined expected lifespan, not an actuarial model. Actuarial tables (e.g., SSA Period Life Tables) account for age, sex, country, and cohort effects. The linear assumption here treats death as a fixed endpoint. For a more grounded input, consult your national statistics office or WHO life tables. The global average is 73.4 years (WHO 2023), but individual variance is enormous - genetics, lifestyle, and healthcare access dominate.

The tool estimates total heartbeats using a constant resting rate of 72 bpm applied across the entire lifespan. In reality, neonatal heart rates exceed 120 bpm, athletes rest at 40-60 bpm, and exercise or stress can push rates above 150 bpm. The 72 bpm figure is a population-median resting average for adults. The estimate is within ±15% for most individuals.

Yes. The JavaScript Date API handles leap years natively (including century rules: divisible by 400). The calculation uses 365.25 days/year for the expected lifespan projection, which is the Julian year average. Time zones are handled by the browser's local clock - all timestamps are relative to your system time.

The tool validates that the birthdate is before the current date. If a future date is entered, the calculation is rejected and a toast notification explains the error. Negative progress values are not meaningful and are blocked at the input validation layer.

Sleep is estimated at 33% of total elapsed time, corresponding to approximately 8 hours per day. This is a lifetime average. Newborns sleep 14-17 hours/day, teenagers 8-10 hours, adults 7-9 hours, and elderly 6-8 hours. The 33% figure is a reasonable weighted average across life stages as published by the National Sleep Foundation.

The tool provides temporal context - how many weeks remain, what percentage is consumed. This data is useful for perspective framing in retirement planning. However, it does not model financial variables. Pair this with actuarial retirement calculators. A key insight: at age 60 with an 80-year expectancy, you have only 1,043 weeks remaining - roughly 20 summers.