# Ecological Footprint & Biocapacity (Earth Overshoot Day) Balance per-capita consumption categories against biocapacity: Earths demanded, surplus/deficit, and Earth Overshoot Day. > Canonical page: https://elysiatools.com/en/tools/ecological-footprint - **Category:** Health - **Keywords:** ecological footprint, biocapacity, earth overshoot day, global hectares, gha, sustainability accounting, one planet living, planetary boundaries, overshoot, carrying capacity human, environmental calculator, resource demand ## Overview Balance five per-capita consumption footprints—food, housing, mobility, goods, and services—against a region’s biocapacity. The calculator returns demand in global hectares (gha), Earths required, ecological surplus or deficit, and Earth Overshoot Day for the population you specify. ## Inputs - **Food footprint (gha/person/yr)** (number): Cropland, grazing, and fishing grounds embodied in your diet. - **Housing footprint (gha/person/yr)** (number): Built-up land plus the energy and forest products behind your home. - **Mobility footprint (gha/person/yr)** (number): Roads, vehicles, and fuel for your transport. - **Goods footprint (gha/person/yr)** (number): Consumables, appliances, clothing — the forest and energy they embody. - **Services footprint (gha/person/yr)** (number): Government, health, education, and other service infrastructure. - **Population (people)** (number): Population sharing this footprint profile — the world, a country, or a city. - **Total biocapacity (gha/yr)** (number): Productive biocapacity of the region (Earth total ≈ 12 billion gha/yr). - **Biocapacity reserved for wild species (%)** (number): Share of biocapacity taken off the human ledger for other species (Half-Earth would use 50). ## When to use - When you need to turn category footprints (gha/person/year) into total demand, Earths, and a surplus or deficit. - When you want Earth Overshoot Day for the world, a country, or another population sharing one lifestyle profile. - When you model how reserving a share of biocapacity for wild species shifts available land, Earths, and the overshoot date. ## How it works - Enter food, housing, mobility, goods, and services in gha per person per year; they sum to footprint per capita. - Set population and total biocapacity (Earth is about 12 billion gha/year). Optionally reserve a percentage for wild species so it is removed from the human ledger. - Demand is compared with remaining biocapacity to report Earths required, deficit or surplus in gha and percent, and Overshoot Day (the day of year when cumulative demand would exhaust annual biocapacity). ## Use cases - World-average accounting: five category shares versus Earth’s ~12 billion gha of biocapacity. - National or city profiles using local population and biocapacity, with or without a wild-species reserve. - One-planet living checks: lower category footprints and a reserve percentage to see whether demand still exceeds available biocapacity. ## Frequently asked questions ### What units do the inputs use? Category footprints are in global hectares (gha) per person per year. Population is people; total biocapacity is gha per year. A global hectare is a hectare of world-average biological productivity. ### How is the number of Earths calculated? Total footprint (per-capita sum times population) is divided by available biocapacity after any wild-species reserve. ### What is Earth Overshoot Day in this tool? The day of the year when cumulative demand would use up that year’s available biocapacity. After that date, demand draws down natural capital. A result of day 365 means demand stays within one year of biocapacity. ### What does the wild-species reserve do? The percentage you enter is taken off total biocapacity before Earths, deficit, and Overshoot Day are computed, so less land is treated as available to people. ### What do the defaults represent? Rough world-average shares: 0.9 + 0.7 + 0.5 + 0.3 + 0.2 = 2.6 gha/person, 8 billion people, and 12 billion gha of biocapacity (about 1.73 Earths and Overshoot Day around 29 July when reserve is 0%). ## Related tools - [Bioavailability Calculator (F = AUC_po · Dose_iv / AUC_iv · Dose_po)](https://elysiatools.com/en/tools/bioavailability-calculator): Calculate the absolute bioavailability F of an extravascular (typically oral) dose: F = (AUC_po · Dose_iv) / (AUC_iv · Dose_po), where AUC_po and AUC_iv are the areas under the concentration-time curve after oral and IV dosing, and the doses correct for any difference in amount administered. F is dimensionless and lies in \[0, 1\]; IV bioavailability is by definition 1, while oral F < 1 reflects incomplete absorption and/or first-pass metabolism. AUC can be in any consistent unit (e.g. mg·h/L) since it cancels out of the ratio. Valid only for linear pharmacokinetics, the same drug molecule, and doses within the linear range. 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