Tiny house and off-grid planning calculator

Rainwater harvesting and cistern sizing

Estimate water captured from a roof and the storage volume required for a defined demand period.

Catchment roof area (m²)Rainfall event (mm)Runoff coefficientFilter/first-flush efficiencyDaily demand (L/day)Storage target (days)Existing tank capacity (L)

Harvest estimate

Captured per event

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Recommended storage

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Existing tank autonomy

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Safety and limitations

This tool provides an early planning estimate only; it is not a permit, certification, safety approval or final engineering design.
Use measured inputs and the exact manufacturer datasheets for the equipment, materials, installation method and operating environment.
Check local building, marine, electrical, gas, water, fire and environmental requirements before construction or installation.
Have a qualified professional verify the final design, protection devices, structure, ventilation, drainage, emergency systems and commissioning tests.
This result does not model every site condition, structural detail, weather event, emergency condition or code requirement.

If an input is unknown or the result is close to a limit, stop and obtain the missing documentation or professional verification.