Water Tank Size Calculator

litres
Average household: 150–250 litres/person/day
days
How many days of supply to store
Construction Updated 16 Jun 2026

Water Tank Size Calculator is a construction estimator that helps you calculate water tank size values from your input data. The formula used is: Required = Persons × DailyUsage × StorageDays; Suggested = round up to nearest 500L. Accepts imperial (feet, inches) or metric (metres, cm) units as labelled on each input.

Formula

Required = Persons × DailyUsage × StorageDays; Suggested = round up to nearest 500L

Example Calculation

Inputs
  • Number of Persons: 5
  • Daily Usage per Person: 200 litres
  • Storage Days: 2 days

Suppose you enter: Number of Persons = 5, Daily Usage per Person = 200, Storage Days = 2. The calculator applies the formula (Required = Persons × DailyUsage × StorageDays; Suggested = round up to nearest 500L) and shows all output values below. Change any input field to immediately see how the result changes.

Frequently asked questions

What is the Water Tank Size?
The Water Tank Size Calculator is a construction estimator that helps you calculate water tank size values from your input data. Accepts imperial (feet, inches) or metric (metres, cm) units as labelled on each input.
When should I use this calculator?
Use this calculator whenever you need a quick, accurate result for water tank size values from your input data without working through the arithmetic manually.
What units should I enter?
Accepts imperial (feet, inches) or metric (metres, cm) units as labelled on each input.
How accurate are the results?
Provides material and dimension estimates. Actual quantities depend on site conditions, waste, and cutting losses.
How do I interpret the result?
Always add a 10–15 % buffer to material estimates to account for waste, cutting errors, and variations in workmanship.
How can I verify the calculation manually?
Use the displayed formula and work through the numbers step by step. If your manual result differs slightly, check rounding and unit conversions first.
Can I use this for planning and budgeting?
Yes. Run best-case, expected, and worst-case inputs to compare outcomes and make safer planning decisions.