Rain Catchment Calculator

How Much Rainwater Can You Harvest?

Use our rain catchment calculator and water usage calculators below
to make the right choice of water tank.

Rain Catchment Calculator

How Much Rainwater Can You Collect?

Struggling to decide which tank suits your needs? Utilise our rain catchment calculator and water usage calculator to simplify your choice! Need more help check our rain catchment calculator faqs

Rain Catchment Calculator

Add in your Roof Size & Annual Rainfall

Local Average Rainfall Guide
Location mm
Brisbane 1200
Toowoomba 724
Sunshine Coast 1478
Gold Coast 1555
Byron Bay 1833

Find the average annual rainfall for your area: Australian Bureau of Metrology

Water Usage Calculator

How much water do you need?

Storage Solutions for Your Rainwater Needs

It’s one thing to know how much rainwater you can collect from your roof, but it’s another to have the means to store it efficiently. At Select, we understand the importance of having a high-quality tank to store your rainwater, ensuring you have a sustainable supply whenever you need it. Whether it’s to keep your garden thriving during dry spells, maintain your home’s water needs, or prepare for drought conditions, having a reliable storage solution is key.

Huge Range, Custom Made, Delivered to your Door

Our extensive range of competitively priced tanks offers the best in design and functionality. Whether you’re in the market for a large round water tank, a space-saving slimline water tank or a discreet under deck tank, Select has you covered. Our tanks are designed to meet diverse needs while providing durability and reliability you can count on.

Experience and Quality

With over 15 years of experience and under the same ownership, Select Water Tanks stands behind the quality of our products. Our stainless steel tanks offer superior strength and longevity compared to cheaper alternatives. Built tough from premium food-grade materials, our tanks are UV stabilized for extended durability, backed by industry-leading an water tank warranty.

When you’re ready to invest in a rainwater storage solution you can trust, Select Water Tanks has the perfect tank for you. Explore our range today and experience the reliability and efficiency of our quality tanks.

Rain Catchment Calculator

Frequently Asked Questions

How do you calculate rainwater catchment?

To calculate rainwater catchment, you can use a simple formula based on the annual rainfall and the surface area of your roof. Here’s how:

Determine Annual Rainfall: Find out the average annual rainfall for your location. This information is typically available from local weather stations or online resources.

Measure Roof Surface Area: Measure the surface area of your roof in square meters (m²) or square feet (ft²). If your roof has multiple sections, measure each section separately and add the areas together to get the total roof area.

Calculate Roof Catchment Capacity: Use the formula:

Annual Rainfall (in millimeters) × Roof Surface Area (in square meters) = Roof Catchment Capacity (in liters)

For example, if your annual rainfall is 1000 mm and your roof surface area is 100 m², the calculation would be:

1000 mm × 100 m² = 100,000 liters

This means your roof can potentially catch 100,000 liters of rainwater annually.

Keep in mind that this calculation provides an estimate of the maximum potential rainwater catchment. Actual results may vary due to factors such as roof design, surface material, runoff efficiency, and water usage patterns.

How do you calculate rainwater tank capacity?
A common rule of thumb is that every square meter of roof space collects about 1 liter of water for each millimeter of rainfall. To estimate your tank capacity, multiply the square meters of your roof area by the average rainfall. This calculation will assist in determining the appropriate tank size for your needs.
What is catchment area in Australia?
The catchment area in Australia refers to the land area where water from rainfall drains into water storage systems. It encompasses the region from which water is collected and channeled into reservoirs or other storage facilities.
How much rain do I need to fill my tank?

To fill your tank, you typically need approximately one litre of water for every 1 millimetre of rain that falls on 1 square meter of roof area. For instance, if you have a roof area of 90 square meters (e.g., 6 meters x 15 meters) and your annual rainfall is 800 millimetres, you would capture around 72,000 litres of water over the year. However, this calculation assumes that your tank is always empty and represents an ideal scenario.