Methodology
Useful estimates need visible assumptions.
LifeTally uses simple, inspectable formulas. Defaults are a starting point, not a claim about one specific person, house or country.
Time and the life clock
Daily hours are multiplied by 365 and shown against a neutral 81-year planning reference. The reference is hidden from the form because it is not a personal lifespan forecast.
Electricity
Energy (kWh) = power in watts ÷ 1,000 × hours used. Cost = kWh × your unit price. Standby adds the number of devices and idle hours.
Bill comparison
After subtracting fixed fees, the calculator finds an effective unit price for each bill. The difference is split into usage, price and fixed-fee effects. Tiered tariffs and taxes can make this approximate.
Household water and leaks
Fixture flow × duration × frequency × household size gives litres. Leak calculations convert drips, litres per minute or litres per hour into annual volume. Your meter remains the best way to verify a real leak.
Body, air and plants
Activity calories use broad metabolic intensity estimates; breathing uses typical ventilation rates; plant oxygen depends heavily on species, leaf area, light and season. These pages are educational comparisons, not health or environmental certification.
Pets
Lifetime cost adds one-time setup to editable monthly and annual care budgets across the chosen number of years. Lifespan, health and local prices vary, so every figure is a planning assumption.
Population, cities, forests and technology
Population and life expectancy use UN series; urbanization uses World Urbanization Prospects; forest area uses FAO; aviation uses ICAO and internet use uses ITU. Every future value is explicitly labelled as a projection or an editable scenario.
Climate
Country charts use World Bank CCKP observed CRU TS4.09 annual temperatures, shown as anomalies from each country's 1951–1980 average. The page compares 1921–1930 with 2011–2020 and estimates the linear trend since 1960; it does not forecast future weather.
Cars and total cost of ownership
Annual car cost adds depreciation, fuel or electricity, insurance, maintenance, tax and registration, parking, tolls and optional finance interest. Country defaults are editable planning scenarios, not live quotes.
Money and countries
Currency changes presentation, not purchasing power. Country budget presets are editable starting examples and should not be treated as live official prices. Actual rent, taxes, healthcare and lifestyle vary widely.
Rounding and dates
Results are rounded for readability. A month means 30 days unless a page states otherwise; a year means 365 days. Methodology last reviewed: 26 August 2026.