Getting Started
What a rain barrel is, how it works, and whether it suits your roof and garden.
Grow a greener garden with rainwater from your roof
Catch roof rainwater in a barrel and water your garden, lawn and ornamental plants — free, soft water, straight from the sky.
Non-potable use only: ornamental garden and lawn watering. Not for drinking, cooking or bathing.
Rain Barrel Calculator
How much rainwater can your roof catch? Enter your roof size and rainfall.
Typical range 75–95%. Losses come from splashing, evaporation and gutter overflow.
Overflow is the storm water left over after your barrels are full.
Results
- Roof area
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- Gallons per inch of rain
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- Gallons per storm
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- Gallons per year
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- Barrels needed to catch one storm
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- Barrels filled by one storm
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- Overflow — water beyond your barrels
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Formula: gallons = roof area (sq ft) × rainfall (inches) × 0.623 × (efficiency ÷ 100). First flush, when on, deducts 10 gallons per 1,000 sq ft from each storm. The yearly total is before first-flush losses, since the number of storms per year varies. 1 gallon = 3.785 litres.
Estimates only — check local rules. Rainwater from this calculator is for non-potable, ornamental garden and lawn use only.
Start here
Setup & Install
Choosing a barrel, placing it, fitting a diverter and linking barrels together.
Troubleshooting
Slow flow, leaks, smells, algae and mosquitoes — fixes that actually work.
Equipment
Barrels, stands, diverters, filters, hoses and screens — what to buy and what to skip.
Latest guides
Rain Barrel for a Small Balcony or Patio
Rain Barrel for a Small Balcony or Patio The best rain barrel for a small balcony or patio is a slim 25 to 35-gallon upright barrel. It holds enough water for pots and a few ornamental beds, fits in a corner without blocking the door, and weighs 200 to 290 pounds when full — heavy, […]
How to Fix a Leaking Rain Barrel Spigot (and Other Leaks)
How to Fix a Leaking Rain Barrel Spigot (and Other Leaks) A leaking rain barrel spigot is usually fixed in 15 minutes with a new rubber washer and a few wraps of plumber’s Teflon tape. Find the leak first — most leaks are at the spigot, not the barrel wall — then drain the barrel […]
How Much Rain Does It Take to Fill a 55-Gallon Barrel?
How Much Rain Does It Take to Fill a 55-Gallon Barrel? It takes only about 0.09 inches of rain on a 1,000 square foot roof to fill a 55-gallon barrel. In other words, a light shower that barely wets the pavement can fill your barrel — as long as your gutters are clean and the […]
Best Rain Barrel for Beginners: 5 Picks Compared
Best Rain Barrel for Beginners: 5 Picks Compared The best rain barrel for beginners is a 55-gallon food-grade plastic drum kit, usually $60 to $90 with the spigot, lid, and overflow fitting included. It holds enough water for a week of watering ornamental beds and a lawn patch, fits beside most downspouts, and is light […]
How Much Money Does a Rain Barrel Save? (Water-Bill Maths, Honest Answer)
A rain barrel saves a little money, slowly. A typical 55-gallon barrel used weekly in the growing season saves about 1,000 to 1,500 gallons a year, which at the average US water price of about 1.5 cents per gallon is about 15 to 25 dollars a year. A barrel that costs 80 dollars therefore takes […]
Rain Barrel Maintenance Checklist: Monthly, Seasonal & Annual Tasks
Rain barrel maintenance takes about 10 minutes a month, and it prevents most barrel problems: smells, mosquitoes, leaks, and clogged spigots. Check the screen, test the spigot, and smell the water once a month. Clean the barrel and the diverter each season. Drain, scrub, and check the seals once a year. That is the whole […]