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How Much Rainwater Can You Collect?

Built by Kevin Glover · @gloverbuilds · Verified formula

Calculate rainwater collection potential from your roof area and local rainfall.

📅 Updated April 2026 ✅ Formula verified 📖 4 min read 🆓 Free · No sign-up

In this article

Rainwater Collection Math
Rainwater Uses

O Cálculo

Litros = área telhado (m²) × chuva (mm) × 0,9. Telhado de 100 m² com 10 mm: 900 litros. Uma cisterna de 1.000 litros se enche com apenas 11 mm de chuva num telhado de 100 m². No Brasil, a pluviosidade é abundante — excelente para captação.

No Brasil

Programa "1 Milhão de Cisternas" no Nordeste demonstrou o impacto. Para residências urbanas: cisternas de 500-2.000 litros para jardim e lavagem. É legal e incentivado — algumas cidades dão desconto no IPTU.

⚡ CalcWolf Insight

A single rain barrel saves approximately 1,300 gallons of tap water per year — about $15-20 on your water bill. The environmental benefit is larger: it reduces stormwater runoff (the #1 source of urban water pollution) by capturing roof water that would otherwise flow into storm drains carrying pollutants to local waterways.

Frequently asked questions

Quanto posso captar?▾

Telhado 100 m² com 1.200 mm/ano de chuva: ~108.000 litros. Uma cisterna de 1.000L se enche rápido.

É legal?▾

Sim — incentivado em muitas cidades. Algumas dão desconto no IPTU para captação de água de chuva.

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Kevin Glover · @gloverbuilds

Founder, CalcWolf · GLVTS · Blickr

All formulas sourced from primary references — IRS publications, peer-reviewed research, and official standards. Results are tested against independent reference calculators before publishing. Rates and brackets updated when official sources change. Editorial policy →