Tap Water Calculator

Tap Water Calculator

Compare the cost of drinking bottled water versus tap water and see how much you could save over time. Enter your daily water consumption, household size, and local prices to calculate daily, monthly, and yearly costs for both options — plus long-term savings over 5, 10, 20, and 50 years.

How tap vs bottled water costs are calculated

Total daily water consumption is the per-person amount multiplied by the number of people in your household:

$$\text{daily liters} = \text{liters per person} \times \text{household size}$$

Tap water cost is straightforward — multiply daily liters by your tap water rate per liter:

$$\text{tap cost} = \text{daily liters} \times \text{cost per liter}$$

Bottled water cost depends on how many bottles you need each day:

$$\text{bottled cost} = \frac{\text{daily liters}}{\text{bottle capacity}} \times \text{cost per bottle}$$

Monthly and yearly figures multiply the daily cost by 30 and 365 days respectively. Annual savings equal bottled yearly cost minus tap yearly cost. The expense ratio shows how many times more expensive bottled water is compared to tap.

Why drink tap water?

In many countries, tap water is safe, regulated, and often contains beneficial minerals. Bottled water can cost thousands of times more per liter — and much of it is simply filtered tap water packaged in plastic. Switching to tap water reduces plastic waste, lowers your carbon footprint, and saves significant money over a lifetime.

Health experts generally recommend about 2 liters of water per day for adults, though needs vary with activity level, climate, and diet. Fruits, vegetables, and other beverages also contribute to daily hydration.

Example calculation

One person drinking 2 liters per day, tap water at $0.001/L, and bottled water in 0.5 L bottles at $1.50 each:

$$\text{tap daily} = 2 \times \$0.001 = \$0.002$$

$$\text{bottled daily} = \frac{2}{0.5} \times \$1.50 = 4 \times \$1.50 = \$6.00$$

$$\text{annual savings} = (\$6.00 - \$0.002) \times 365 \approx \$2{,}189$$

Over 10 years, that is nearly $22,000 saved — and bottled water would be about 3,000× more expensive than tap. For related water tools, see the Drip Faucet Calculator, Water Intake Calculator, and Rainwater Collection Calculator.