When to use this calculator
Estimate water use for repeated timed activities such as showers. Use a measured flow rate to improve the estimate.
Explore the water use & conservation calculators for other questions in this topic. For a related calculation, use the Appliance Annual Cost Calculator: Estimate annual electricity spending for a constant-power appliance.
PUTTING IT INTO PRACTICE
Water Use: a worked example
The values below are an illustrative example, not a recommendation. Replace them with measurements or assumptions that match your question.
| Input | Example value |
|---|---|
| Flow rate (L/min) | 8 |
| Minutes per activity | 10 |
| Activities per day | 2 |
| Result | 160 litres/day |
- Check the input labels and enter the example values above.
- Apply the relationship: Daily water = flow × duration × daily activities.
- The result is 160 litres/day, rounded for display.
How to interpret your result
Use a measured flow rate to improve the estimate.
Use measured flow rates when possible. A rainfall volume estimate is not a storage simulation and can exceed tank capacity. Fixed water charges and sewerage charges may follow separate tariff rules.
Frequently asked questions
Can rain collected exceed tank capacity?
The geometric collection estimate can. Storage, overflow, first-flush diversion and use during rainfall need a separate tank model.
How do I use the water use calculator?
Enter flow rate (l/min), minutes per activity, activities per day. The result updates automatically. Use the units shown beside each input; the example values illustrate the method.
Which formula does this calculator use?
Daily water = flow × duration × daily activities.
What should I check before using the result?
Use a measured flow rate to improve the estimate.
How are results rounded?
Scalar numbers display up to six decimal places, with scientific notation for very large or small values. Text, fraction, date and schedule outputs use the format described on the tool. Intermediate calculations use JavaScript floating-point arithmetic. Keep sensible precision for your measurements.
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