Free tool
Rainwater harvesting calculator
How much water can your roof collect in a year? Estimate the harvest and what it covers.
Rainwater harvesting estimator
- Harvestable per year
- 0 L
- In kilolitres
- 0 kL
- Household use covered
- 0 days
An estimate of the potential, assuming the rain is collected and stored. Real collection depends on how rain falls across the year, first-flush losses and tank size.
How this works
Harvest (litres) = roof area (m²) × annual rainfall (mm) × runoff coefficient. One millimetre of rain on one square metre is one litre. The runoff coefficient (about 0.75 to 0.9) accounts for water lost to evaporation, splash and first-flush. Rainfall defaults to a rounded figure for Raipur; use your local figure if you know it.
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Common questions
About this tool
How much rainwater can I collect from a 1,000 sq ft roof?
1,000 sq ft is about 93 m². At 1,200 mm of rain and a coefficient of 0.8, that is roughly 89,000 litres a year, though actual collection depends on how the rain falls across the year and how much your tank can hold.
What do I need for rainwater harvesting?
Gutters or downpipes from the roof, a first-flush diverter and filter, and a storage tank or a recharge pit. We supply the pipes, fittings and tanks.
Is the water safe to drink?
Harvested rainwater is normally used for gardening, flushing, cleaning and recharge unless it is properly filtered and treated for drinking.
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Turn these numbers into a quote
Share a few details and we will come back with brand options and a quotation. Prefer to talk? Call or message us.
- +91 98268 56322
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- info@keshripipes.com
- Ramnagar, Raipur, Chhattisgarh 492001