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Water Tank Size Calculator

Herritech engineering teamUpdated 4 October 20263 min read

Water Tank Size Calculator
Pictured: 10,000-litre water storage tank.
Quick answer: Tank size = daily water use × days of storage. Daily use = people × litres per person per day + other uses (animals, garden, cleaning). For example, 6 people using 50 litres each plus 100 litres for other uses need 400 litres a day; for 3 days of storage that is 1,200 litres, so a 1,500-litre tank fits. Use the calculator with your own figures.
Key facts
  • Storage = daily use × days of storage
  • Daily use = people × litres each + other uses
  • Choose the next tank size up
  • Supply interruptions decide how many days you need
On this page
  1. Water Tank Size Calculator
  2. How Much Water Does a Person Use?
  3. How Many Days of Storage?
  4. Tank Sizes and Prices
  5. Frequently asked questions

Water Tank Size Calculator

Example figures only: replace them with your own. Results update as you type.

Daily use (litres)–
Storage needed (litres)–
Number of 10,000 L tanks–

How Much Water Does a Person Use?

Use depends on whether the home has flushing toilets, showers and a washing machine. See how much water a family uses per day for a breakdown, and measure your own use from a water bill if you can.

How Many Days of Storage?

Match it to how often supply fails. If county water comes twice a week, store at least three or four days. Boreholes with a pump need less storage, but a reserve helps during power cuts.

Tank Sizes and Prices

Current listed prices incl. VAT (updated 4 October 2026).

Choose the next size up from the calculator. For refill shops see storage for refill stations; for the full list, tank price list.

Watch: Fabrication and components

H-TECH high-pressure bottle rinsing machineVideo · 0:26 · Herritech Ventures on YouTube
H-TECH stainless steel storage tank productionVideo · 0:30 · Herritech Ventures on YouTube

Frequently asked questions

How do I calculate the size of a water tank?

Multiply your daily water use by the number of days of storage you want.

What size water tank does a family of 6 need?

At about 50 litres each plus other uses, around 400 litres a day; for three days, a 1,500-litre tank. Use your own figures.

How many litres of water does a person use per day?

It varies widely with toilets, showers and appliances; check your water bill or the guide linked above.

How many litres does my water tank hold?

For a round tank: 3.14 × radius² × height in metres × 1,000 gives litres; the size is also usually printed on the tank.

How much is a 10,000 litre water tank in Kenya?

Our 10,000-litre tank is KSh 68,000.

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