Tap Water Calculator — Usage & Cost
Find out exactly how much tap water your household uses and what it costs. Enter daily litres per person, the number of people in the household, and your water tariff rate to see daily, weekly, monthly, and annual figures at a glance.
L/day
per m³
Based on 54,750 L/year (54.8 m³)
- 1
Total daily household usage
150 × 1 = 150 - 2
Annual water volume (L)
150 × 365 = 54,750 - 3
Annual usage in m³
54,750 ÷ 1000 = 54.751 m³ = 1000 L; water utilities charge by the cubic metre. - 4
Annual cost
54.75 × 2.5 = 136.88
How does this calculator work?
Annual tap water cost = (L/day/person × people × 365 ÷ 1000) × tariff per m³. A household of 2 people each using 150 L/day at $2/m³ spends about $219/year. The monthly figure is useful for budgeting; total m³/year appears on your annual bill.
Formula
How this is calculated
Water utilities charge by the cubic metre (m³), where 1 m³ = 1000 litres. This calculator multiplies per-person daily usage by household size to get the total daily household draw, then scales up to weekly, monthly (using an average 30.44 days/month), and annual figures. Cost is derived by dividing the volume in litres by 1000 to convert to cubic metres, then multiplying by the tariff rate.
Typical per-person daily usage varies widely: the WHO recommends 50–100 litres for basic hygiene needs, but residents in developed countries typically use 120–300 litres per day when accounting for showering, toilet flushing, laundry, dishwashing, and outdoor use. Your water bill will state the volumetric tariff, often as a tiered rate — use the average blended rate (total bill ÷ m³ consumed) if the tariff has multiple tiers.
This calculator covers potable (drinking/tap) water costs only. It does not include fixed service or standing charges that most utilities also bill, nor wastewater/sewerage fees, which are often charged as a percentage of water consumed.
Frequently asked questions
In developed countries, average per-capita daily indoor water use is roughly 100–300 litres. Showers (8–65 L), toilet flushing (6–13 L per flush), laundry (50–150 L per load), and dishwashing (6–20 L) are the biggest contributors. The WHO minimum for basic needs is 50 L/day.
Your tariff is on your water bill, usually shown as a rate per cubic metre (m³) or per 1000 litres. Typical rates range from about $0.30/m³ in low-cost regions to $4–5/m³ in expensive cities. If your tariff is tiered, use the blended average: total volumetric charge ÷ m³ consumed.
No — it covers volumetric water consumption only. Most bills also include a fixed standing/service charge and a wastewater fee (typically 60–120% of the water charge). Check your bill for these extras and add them separately to get the full cost.
Also known as
TG we-Calculate Editorial Team. (2026). Tap Water Calculator — Usage & Cost [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/tap-water-calculator
TG we-Calculate Editorial Team. "Tap Water Calculator — Usage & Cost." TG we-Calculate. 2026. https://we-calculate.com/calculator/tap-water-calculator.
TG we-Calculate Editorial Team, "Tap Water Calculator — Usage & Cost," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/tap-water-calculator
@misc{wecalculate_tap_water_calculator, title = {Tap Water Calculator — Usage & Cost}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/tap-water-calculator}}, year = {2026}, note = {TG we-Calculate} }
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