# How do you calculate gutter size?

## How do you calculate gutter size?

How To Do It. Multiply the surface area by the pitch factor to find the rain collection area for your roof and you can buy the right size guttering. In plastic K Style, 5 inch guttering will drain up to 5520 ft², 6 inch up to 7960 ft². In Half Round the capacities are 2500ft² for 5 inch and for 6 inch, 3840ft².

### How many downpipes do you need for a roof?

To calculate the minimum number of downpipes, divide the roof catchment area by the allowable maximum catchment per downpipe. To calculate the average catchment per downpipe, divide the roof catchment area by the number of downpipes.

How do you calculate rainwater runoff from a roof?

To calculate the runoff from any given rainfall:

1. Take the dimensions of the footprint of your roof and convert them to inches. (So, a 50′ x 20′ roof is 600″ x 240″.)
2. 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.)

What is the minimum slope of roof gutters?

Cost of Rain Gutters To ensure that gutters drain properly, make certain they slope (½ inch for every 10 feet) toward a downspout. For gutter runs longer than 40 feet, it’s best to pitch the gutter down from the middle to a downspout at each end.

## How do I calculate roof drainage?

Take the roof’s total square footage and divide by the total square footage handled by one drain. The result is the number of drains needed. For example: 50,000 / 4,400 = 11.36; or 12 drains required.

### What is the proper slope for rain gutters?

½ inch
Cost of Rain Gutters To ensure that gutters drain properly, make certain they slope (½ inch for every 10 feet) toward a downspout. For gutter runs longer than 40 feet, it’s best to pitch the gutter down from the middle to a downspout at each end.

What size gutters are best?

On average, the 5-inch (12.7 cm) system will suffice. For large houses or when there are a number of trees near the roof that will shed leaves, a 6-inch (15.3-cm) gutter width is typically best. Gutter shape is important as well but is mostly a matter of personal preference.

What size gutters do you need?

The bigger your roof and the more rain you get, the bigger the gutters you’ll need. The most common residential gutter size is five inches. For downspouts , a good rule is one for every 40 feet of gutter.

## How much slope does gutter need?

Measure the length of gutter needed. The minimal slope needed for proper gutter drainage is 1.25 cm (1/4 inch) for every 3 metres (10 feet) of gutter.