# Frequent question: How do I calculate how much water my roof holds?

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## How do you calculate rainwater collection on a roof?

Roughly speaking, 1 millimetre of rain over 1 square metre of roof equals 1 litre of water. This capacity can be calculated using the following formula: Annual rainfall (in millimetres) x Roof surface area (in square metres) = Roof catchment capacity.

## How do you calculate rainwater volume?

Formula: Area (Length x Width) x Rainfall

1. A = Length of the roof area.
2. B = Width of the roof area.
3. C= The amount of rainfall in inches.
4. The formula is A x B x C = Water Volume.

## How many gallons are in an inch of rain per square foot?

2. Every square foot of roof space collects . 6 gallons of water in a 1 inch rainfall.

## How do I calculate the square footage of my roof?

Multiply the length by the width to find the area of rectangular sections.

1. If a section is 120 feet (37 m) x 100 feet (30 m), its total square footage would be 12,000 square feet (1,100 m2).
2. Be sure to find the area of any dormers on your roof, as well.
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## How much water comes off my roof when it rains?

When you look at the numbers, it’s surprising how much water you can collect every time it rains. Just a half inch of rain falling on a 1,000-square-foot roof will yield 300 gallons of water.

## How much roof does it take to fill a tank?

As a general rule of thumb, each square metre of roof space collects around 1 litre of water for every 1 millimetre of rainfall received. Using the calculation of (x) square metres of roof space available for connection to your tank multiplied by the amount of rainfall will help guide your decision.

## How many Litres is 1mm of rain?

With a rainfall of 1 mm, every square metre receives 1 litre of rain water. A rainfall of 1 mm supplies 0.001 m3, or 1 litre of water to each square metre of the field. Thus 1 ha receives 10 000 litres.

## How do you calculate runoff factor?

For a given surface area such as a roof or yard, multiply the area by the inches of rainfall and divide by 231 to obtain the runoff in gallons. The factor 231 comes from the fact that the volume of 1 gallon equals 231 cubic inches.

## How do you convert inches of rain to volume?

Multiply the roof dimensions by the number of inches of rainfall. (In this example, 600″ x 240″ x 1″ = 144,000 cubic inches of water.)

## How many gallons is 2 inches of water?

I read somewhere, 2 inches = 2 gallon. Another article says 4-5 gallons per week in hot weather. One may also ask, what does it mean to water 1 inch?

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## Is 1 to 2 inches of rain a lot?

1/2 (0.5) of an inch of rain – A light rain never reaches this amount, moderate rain for 1-2 hours or heavy rain for 30-45 minutes. … One (1.00) inch of rain – A light moderate rain never reaches this amount, heavy rain for several hours (2-5 hours). There would be deep standing water for long periods of time.

## How many inches of rain does it take to fill a 5 gallon bucket?

5 gallons is about 2/3 of a cubic foot, and 2 inches is 1/6 of a foot. 2/3 cubic feet divided by 1/6 feet is 4 square feet, so 2 inches of rain falling over an area of 4 square feet is enough to fill a 5-gallon bucket.

## Is the square footage of a house the same as the roof?

Roofing Quote Footage is Not the Same as Home Square Footage

Depending on where the information is coming from is going to determine the basis on which the estimated roof footage is calculated. The roof square footage is what we (roofing contractor) need to calculate a budget quote to do the job.

## How do you estimate roofing?

To estimate how many shingles you’ll need, first estimate the total square footage of your roof’s surface. To do this, measure the length and width of each plane on the roof, including dormers. Then, multiply length x width to get the square footage of each plane.

## How do you calculate roofing?

Roof surfaces are measured in “squares”. A roofing square is equal to 100 square feet of the roof. To determine the number of squares on the gable roof example in this post, divide its total of 2400 square feet by 100 (2400 ÷ 100 = 24). This means you would need 24 squares of shingles to cover that roof.

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