Calculadora de Caixa d'Água
- Created by
- Renato Passos, Eng. de Software
- Reviewed by
- Renato Passos, Eng. de Software
Last updated: Apr 18, 2026
Formula
volume = moradores × consumo/dia × dias_reserva
About this calculator
The Water Tank Calculator helps you determine the ideal reservoir size for your home, considering the number of residents, daily consumption per person, and reserve days. The formula is: volume = residents × consumption/day × reserve days. The standard consumption is 200 liters per person per day, with a 2-day reserve, as per technical recommendations for residences.
You can adjust consumption and reserve days as needed. For example, in areas with frequent water shortages, increase reserve days. For homes with higher usage (pool or garden), daily consumption may be higher. The calculator provides volume in liters, which can be converted to cubic meters (divide by 1000).
When to use? When planning home construction or renovation, to specify the water tank size. Also useful to check if an existing tank meets demand, especially during rationing. Note that NBR 5626 recommends at least 24 hours of reserve, but 2 days is a safe margin.
Cautions: The calculation considers only human consumption. If using water for irrigation, car washing, or pool, add those volumes separately. Also check water pressure and tank height for proper supply. This calculator does not replace a complete hydraulic design, but serves as an initial estimate.
Frequently asked questions
How many liters of water tank are needed for a 4-person house?
Considering 200 liters per person per day and 2 days of reserve, the volume is 4 × 200 × 2 = 1600 liters. Round up to a commercially available size, such as 1500 or 2000 liters.
Can I use the calculator for buildings or businesses?
Yes, but adjust daily consumption per use. For offices, 50 liters per person may suffice. For buildings, also consider fire reserve requirements.
What if the water tank is too small?
You can install a second tank in parallel or replace with a larger one. Check the support structure and piping before increasing capacity.
What is the difference between liters and cubic meters?
1 cubic meter equals 1000 liters. To convert liters to m³, divide by 1000. Example: 2000 liters = 2 m³.
Does the calculator account for losses or leaks?
No. The calculation is for estimated consumption. It is recommended to add 10% to 20% for losses and contingencies, especially in systems with pumping.